Sheng San Li

University of Florida | UF · Department of Electrical and Computer Engineering

A numerical simulation of the performance of CIGS solar cells has been carried out using the AMPS-1D device simulation program to study the sensitivity of cell performance (efficiency, photo-J-V, and QE characteristics) on material parameters. The simulation results suggest that the carrier mobility, recombination center density, and carrier densit...

Photonic devices play an important role in a wide variety of applications in the areas of photovoltaic (PV) power generation, optical communications, data transmission and signal processing, detection, sensors and optical imaging, and displays and light sources. Recent advances in III-IV compound semiconductor growth and processing technologies hav...

The invention of germanium alloy bipolar junction transistors (BJTs) by Bardeen, Brattain, and Shockley in 1948 has revolutionized the electronics industry. The BJT device is considered one of the most important electronic components used in modern integrated circuit (IC) chips for computers, communications and power systems, and in many other digi...

Rapid thermal annealing (RTA), with fast ramp rate, was performed on several Cu(In,Ga)Se2 (CIGS) films and solar cells under various peak annealing temperatures and holding times. Characterizations were made on CIGS films and cells before and after RTA treatments to study effects of RTA on the CIGS film properties and cell performance. In addition,...

Cu(In,Ga)Se₂ (CIGS) and CuGaSe₂ (CGS) solar cells were fabricated using Cd_1-xZn_xS (CdZnS) buffer layers prepared by chemical bath deposition (CBD) with relative Zn compositions in the CBD bath values of X_bath=0 (i.e., pure CdS), 0.1, 0.2, 0.3, 0.4, and 0.5. The cell performance parameters of CI...

Pulsed non-melt laser annealing (NLA) has been used for the first time to modify near-surface defects and related junction properties in Cu(In,Ga)Se2 (CIGS) solar cells. CIGS films deposited on Mo/glass substrates were annealed using a 25ns pulsed 248nm laser beam at selected laser energy density in the range 20–60mJ/cm2 and pulse number in the ran...

A two-stack multi-color quantum dot infrared photodetector (QDIP) for detection in the 8–12 μm spectral window was introduced. The top stack was made up of 8 periods of In0.5Ga0.5As/GaAs QDs, and the second stack consists of 8 periods of InAs/GaAs QDs, and a 500 Å GaAs spacer was used for each period in both stacks. A photoresponse peak around 7.9–...

The performance of the chalcopyrite material Cu(In,Ga)Se2 (CIGS) used as an absorber layer in thin-film photovoltaic devices is significantly affected by the presence of native defects. The deep-level transient spectroscopy (DLTS) technique is used in this work to characterize the defect properties, yielding relevant information about the defect ty...

Device modeling and simulation studies of a Cu(In1−x,Gax)Se2 (CIGS) thin film solar cell have been carried out. A variety of graded band-gap structures, including space charge region (SCR) grading, back surface region grading, and double grading of the CIGS absorber layer, are examined. The device physics and performance parameters for different ba...

In this paper we report a high performance two-stack, multi-color quantum well infrared photodetector (QWIP) composed of an InGaAs/AlGaAs QWIP and an InGaAs/AlGaAs/InGaAs triple-coupled (TC-) QWIP grown on the GaAs substrate for mid- and long-wavelength (MW/LW) infrared (IR) detection. The basic device structure consists of a MWIR QWIP stack with 3...

A high-sensitivity In _0.6 Ga _0.4 As/GaAs quantum-dot infrared photodetector (QDIP) with detection wave band in 6.7–11.5 μm and operating temperature up to 260 K under normal incident illumination has been demonstrated. The peak detection wavelength shifts from 7.6 to 8.4 μm when the temperature rises from 40 to 260 K. The back...

Type-II superlattices (SLs) based on InAs/GaInSb material systems have been theoretically investigated and optimized to achieve large valence band splitting and thin constituent layers, which are desirable for high detectivity and large absorption coefficient for the long-wavelength infrared (LWIR) and very long-wavelength infrared (VLWIR) detectio...

A novel InAs/GaAs quantum-dot infrared photodetector with an In_0.5Ga_0.5P dark current blocking layer for long-wavelength infrared (LWIR) detection has been developed in this work. Very low dark current densities were obtained at V_b = - 0.5 V (10^-10 A/cm^-2) and V_b = + 0.5 V (10<sup>-1...

Quantum well infrared photodetectors (QWIPs) have been widely investigated for the 3–5 μm mid-wavelength infrared (MWIR) and 8–12 μm long-wavelength infrared (LWIR) atmospheric spectral windows as well as very long wavelength infrared (VLWIR: λ c > 14 μm) imaging array applications in the past decade. The mature III-V compound semiconductor growth...

A high-performance three-stack, three-color quantum-well infrared photodetector for the mid-, long-, and very long-wavelength infrared detection has been developed in this work. The detection bandwidths with full-width at half-maximum are 5.9–7.0, 9.1–11.2, and 12.2–16.9 μm, which cover the major portion or entire range of the three atmospheric blo...

A high performance InGaAs/GaAs/AlGaAs superlattice coupled (SC) quantum well infrared photodetector (QWIP) grown on GaAs has been developed for long wavelength infrared detection. The dark I-V and spectral response were measured and analysed on this device. Excellent responsivity and detectivity were obtained for this SC-QWIP. The peak detectivity...

The alternative buffer layer material Inx(OH,S)y was deposited on Cu(In,Ga)Se2 (CIGS) thin films by chemical-bath-deposition (CBD). The impurities in Inx(OH,S)y buffer layers and their atomic concentration were characterized by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) analyses. In addition, AES was used to depth...

A new δ -doped In0.24Ga0.76As/GaAs pseudomorphic high electron mobility transistor (HEMT) using a graded superlattice spacer grown by molecular beam epitaxy (MBE) has been successfully fabricated and investigated. The present device structure demonstrated a more than 40% enhancement of electron mobility and 20% higher product value of electron mobi...

Quantum well infrared photodetectors (QWIPs) have been widely investigated for the 3–5 μm mid-wavelength infrared (MWIR) and 8–12 μm long-wavelength infrared (LWIR) atmospheric spectral windows as well as very long wavelength infrared (VLWIR: λc 14 μm) detection in the past decade. The mature III-V compound semiconductor growth technology and the d...

The design, fabrication and characterisation of a high performance double barrier (DB) AlGaAs/InGaAs/AlGaAs linear-graded barrier (LGB) quantum well infrared photodetector (QWIP) is reported for 8-10 μm detection. Broadband detection under positive bias and normal spectral response under negative bias conditions were observed in this device due to...

We report two high-performance quantum-well infrared photodetectors (QWIPs) using GaAs/AlGaAs digital graded superlattice barriers and InGaAs quantum wells for long-wavelength infrared and broadband (BB) detection. The compositionally digital graded superlattice barriers (DGSLBs) of the QWIP structures were grown using GaAs/AlGaAs digital graded su...

In this paper the intersubband optical transitions in quantum dots are studied. Theoretical calculations of peak wavelengths and oscillator strengths of the transitions from the bound to first and second excited states were made for the InxGa1−xAs/GaAs and InAs/AlxGa 1−xAs systems. The results show that transition from the ground to the first excit...

The design of five broadband quantum well infrared photodetectors (BB-QWIP) sensitive over the range of 7 to 14 μm spectral range is reported. Three n-type BB-QWIPs consisting of three, four, and five QW of different thickness and/or composition in a unit cell, which are then repeated 20 times for the three and four QW devices and three times for t...

A high-performance n-type AlAs/InGaAs/AlAs/InAlAs double-barrier quantum well infrared photodetector grown on InP with photovoltaic (PV) and photoconductive (PC) dual-mode operation has been fabricated and characterized in this work. The PV and PC detection scheme employs the intersubband transition from the ground bound state to the quasibound exc...

A four-color quantum well infrared photodetector (QWIP) has been demonstrated in this work. Four stacks of quantum well structures with four different detection wavelengths are sandwiched among three highly doped contact layers. The peak wavelengths of the four colors are centered at 4.7, 8.5, 9, and 12.3 μm. The 4.7 and 8.5 μm stacks are separated...

Typical quantum-well infrared photodetectors (QWIPs) exhibit rather narrow spectral bandwidths of 1–2 μm. For certain applications, such as spectroscopy, sensing of a broad range of infrared photons is necessary. In this letter, we report on the design of two p-type broadband (BB) QWIPs for detection in the 7–14 μm long-wavelength infrared band. Tw...

A normal incidence p-type compressively strained layer superlattice (SL) In0.27Ga0.73As/Al0.15Ga0.85As quantum well infrared photodetector with a spectral response peak at 19.2 mum and a cutoff wavelength lambdac>20 mum under moderate background illumination have been demonstrated in this work. A responsivity of 50 mA/W and a gain-quantum efficienc...

Rapid progress in quantum well IR photodetectors (QWIPs) technology has made it possible to develop large format, and high uniformity QWIP focal plane arrays (FPAs) for IR imaging sensor applications. So far, all QWIP FPAs are made of n-type GaAs/AlGaAs material systems grown on GaAs substrates due to the maturity of this material system and excell...

Quantum well infrared photodetector (QWIP) technology has developed rapidly in the past decade culminating in the demonstration of large format focal plane arrays. Most of the efforts so far have been on tactical applications in which an increased operating temperature is the major objective. For strategic applications with a cold background and a...

A high sensitivity triple-coupled quantum well infrared photodetector (TC-QWIP) based on high strain InGaAs/AlGaAs/InGaAs material system has been demonstrated. It consists of a high strain Si-doped In0.25Ga 0.75As quantum well and two undoped thin Al0.11Ga 0.89As/In0.12Ga0.88As quantum wells (QWs) separated by a thick Al0.11Ga0.89As barrier layer....

In this research project, we have conducted theoretical and experimental studies on normal incidence absorption in n-type direct gap QWIPs. A theoretical model for calculating the TE to TM transition ratios for the symmetrical LWIR- and step MWIR-QWIPs has been developed in this work. The role of strain on the normal incidence absorption has been i...

We present a study of several n- and p-type strain-layer quantum well infrared photodetectors (SL-QWIPs) using InxGa1-xAs/ALGa1-yAs grown on GaAs and InxGa1-xAs/InyAl1-yAs on InP substrates. The results show a significant improvement in device performance for these devices over the unstrained QWIPs. The devices studied include a high-strain (HS-) n...

Intersubband transitions using normal incidence in the conduction band of a direct gap semiconductor quantum well structure is very unconventional, yet very useful in quantum well infrared photodetectors (QWIPs). On the other hand, normal incidence absorption is allowed in both p-type QWIPs and indirect bandgap n-QWIPs. However, the low electron ef...

We report a two-stack indirect-barrier (IB-) GaAs/Al(subscript 0.55)Ga(subscript 0.45)As quantum well infrared photodetector (QWIP) for mid-wavelength infrared (MWIR) and a voltage-tunable In(subscript 0.05)Ga(subscript 0.95)As/GaAs/Al(subscript 0.19)Ga(subscript 0.81)As triple-coupled (TC-) QWIP for long-wavelength infrared (LWIR) detection. We al...

Rapid progress in III–V semiconductor quantum well infrared photodetectors (QWIPs) has made it possible to develop large area, uniform, high performance GaAs/AlGaAs QWIP focal plane arrays (FPAs) for staring imaging arrays applications. This paper presents the recent developments of single- and multi-color QWIPs for detection in the 3–5 μm and 8–14...

A very high performance two-stack, two-color, high strain (HS-) quantum well infrared photodetector (QWIP) has been demonstrated. The sample was grown on a semi-insulating (100) GaAs by molecular beam epitaxy (MBE). It consists of two stacks of MWIR and LWIR QWIPs as the active region with a 100 nm thick highly doped contact layer grown between the...

A contactless dual-beam optical modulation (DBOM) technique [Y. S. Chang and S. S. Li, Solid-State Electron., 1995, 38, 297–304, Y. S. Chang, S. S. Li and P. C. Yang, Solid-State Electron., 1995, 38, 1359–1366] was employed to determine the interface recombination velocities and substrate carrier lifetimes in the SIMOX SOI wafers processed under di...

In this research project, we have demonstrated several novel strained layer p-type quantum well infrared photodetectors (QWIPs) for the 3-5 um mid-wavelength infrared (MWIR) and 8-14 um long-wavelength infrared (LWIR) detection. These normal incidence p-QWIPs employed the tensile and compressive strained layer quantum well structures to enhance the...

Investigation of two p-type compressively-strained layer (PCSL) InGaAs/AlGaAs/GaAs quantum well infrared photodetectors (QWIPs) grown on (1 0 0) semi-insulating (SI) GaAs substrate has been carried out. The first detector uses a step-bound-to-miniband (SBTM) transition scheme for long wavelength infrared (LWIR) detection and has a detection peak at...

A high strain two-stack, two-color, InGaAs/AlGaAs and AlGaAs/GaAs quantum well infrared photodetector for midwavelength infrared (MWIR) and long wavelength infrared (LWIR) detection has been demonstrated. Each stack is designed to have detection in one of the two atmospheric windows, 3–5 μm and 8–12 μm, respectively. The MWIR stack has employed 35%...

A voltage‐tunable multicolor triple‐coupled quantum‐well infrared photodetector (TC‐QWIP) has been developed for 8–12 μm detection. The TC‐QWIP consists of three coupled quantum wells formed by an enlarged Si‐doped InxGa1−xAs quantum well and two undoped GaAs quantum wells separated by two thin AlyGa1−yAs barriers. Two TC‐QWIP structures with varyi...

Investigation of a InGaAs/AlGaAs/GaAs p‐type step bound‐to‐miniband compressively strained layer quantum well infrared photodetector grown on (100) semi‐insulating GaAs has been made. A long wavelength infrared detection peak at 10.4 μm with a full width at half‐maximum bandwidth, Δλ/λp=20% was obtained for this detector. The measured spectral peak...

Analytical models valid in weak, strong and moderate inversion regions are derived for the gate-all-around (GAA) nMOS silicon-on-insulator (SOI) MOSFETs. The non-ideal GAA MOSFETs was modeled as a parallel connection of one long-double-gate and two edge-gate transistors. Using Poisson's equation which considers both the depletion charges and minori...

Device operation under low applied bias voltage has been examined for both p-type and n-type quantum well infrared photodetectors. Under low electric fields and at low temperatures, the carrier lifetime in the quantum well bound states is large compared to the intrawell carrier scattering time, allowing the carriers to thermalize in the heavily dop...

Two p-type compressively strained-layer (PCSL) InxGa1−xAs/AlyGa1−yAs (where,x=0.4, 0.2;y=0, 0.15) quantum well infrared photodetectors (QWIPs) grown by MBE on (100) semi-insulating (SI) GaAs substrates have been investigated for 3-5 μm MWIR and 8-14 μm LWIR imaging arrays applications. The In0.4Ga0.6As/GaAs PCSL-QWIP utilizing the resonant transpor...

Dark current noise measurements between 10¹ and 10⁵ Hz were carried out on a compressively strained p‐type InGaAs/AlGaAs quantum‐well infrared photodetector as a function of temperature and bias voltage. The measured noise can be attributed to number fluctuation noise associated with the generation and recombination of holes f...

A novel contactless dual-beam optical modulation (DBOM) technique has been employed for determining the interface recombination velocities and substrate carrier lifetimes in a SIMOX (Separation by IMplantation of OXygen) wafer. The DBOM method utilizes the optical modulation of the transmitted light intensity of an infrared (i.r.) probe beam (hv <...

Dark current noise measurements between 10 and 10⁵ Hz were carried out at T=77 K on three different types of III‐V quantum‐well infrared photodetectors designed for 8–12 μm IR detection. These devices have superlattice barriers leading to miniband transport in the extended conduction band. For frequencies between 10² and 10<su...

During this reporting period, we have made excellent progress towards the program goals. A significant achievement was made in the development of a new compressionally strained p-type GaAs/InGaAs QWIP grown on GaAs by MBE. This new QWIP achieved two color detection with detective peaks at 8.9 um an 8.4 micrometers in the LWIR band and 5.5 micromete...

A new contactless dual-beam S-polarized reflectance (DBSPR) technique has been developed for measuring the top Si film and buried oxide thickness in a SIMOX (Separation by IMplantation of OXygen) wafer. Top Si film and buried oxide thicknesses of the SIMOX wafers ranging from 0.2 to 1.6 μm and 0.36 to 0.44 μm, respectively, were determined using th...

A normal incidence p‐type compressive strained‐layer In 0.4 Ga 0.6 As/GaAs quantum well infrared photodetector (PSL‐QWIP) grown on (100) semi‐insulting GaAs substrate with molecular beam epitaxy technique for 3–5 μm mid‐wavelength infrared and 8–14 μm long‐wavelength infrared detection was demonstrated for the first time. This PSL‐QWIP shows a broa...

A normal incidence p-type compressive strained-layer In(0.4)Ga(0.6)As/GaAs quantum well infrared photodetector (PSL-QWIP) grown on (100) semi-insulting GaAs substrate with molecular beam epitaxy technique for 3-5 micrometer mid-wavelength infrared and 8-14 micrometer long-wavelength infrared detection was demonstrated for the first time. This PSL-Q...

A new two‐color n‐type GaAs/AlAs/AlGaAs double barrier quantum well (DBQW) and bound‐to‐miniband GaAs/AlGaAs quantum well infrared photodetector (QWIP) with photovoltaic (PV) and photoconductive (PC) dual‐mode operation in the 3–5 and 8–14 μm atmospheric spectral windows has been demonstrated in this work. It consists of a stack of the midwavelengt...

Dark current noise measurements on a bound to miniband transition quantum well infrared photodetector were carried out at 77 K to either prove or disprove the correctness of three different, recently published noise expressions. The noise data indicate that the bound electron generation rate varies exponentially with applied voltage.

A numerical analysis of the grating coupling for a two‐dimensional circular aperture mesh metal grating coupled GaAs quantum well infrared photodetector (QWIP) has been carried out. The inner products of Floquet modes and waveguide modes were derived in a simple analytic form. Using the normalized wavelength and normalized aperture radius, two sets...

An ultra-low dark current normal incidence p-type strained-layer In0.3Ga0.7As/In0.52Al0.48As quantum well IR photodetector (PSL-QWIP) grown on semi-insulating (100) InP substrate by MBE technique has been demonstrated for the first time. This PSL-QWIP shows a background limited performance (BLIP) for T≤100 K, which is the highest BLIP temperature e...

An ultralow dark current normal incidence p‐type strained‐layer In 0.3 Ga 0.7 Al/In 0.52 Al 0.48 As quantum well infrared photodetector (PSL‐QWIP) grown on (100) semi‐insulating InP substrate by molecular beam epitaxy technique for 8–12 μm infrared detection was demonstrated for the first time. This PSL‐QWIP shows background limited performance (BL...

Numerical analysis of a two‐dimensional (2D) square mesh metal grating coupler formed on top of a bound‐to‐miniband (BTM) transition GaAs‐based quantum‐well infrared photodetector (QWIP) has been carried out. Two normalized parameters s and h (i.e., s=λ/g and h=a/g, where g is the grating period and a is the width of the aperture) are used in the s...

We report four novel III-V quantum well infrared photodetectors (QWIPs) fabricated on the MBE grown n-type GaAs/AlGaAs, AlAs/AlGaAs, and p-type strained layer (PSL) InGaAs/InAlAs material systems. The detection schemes for these QWIPs are based on bound-to-continuum (BTC) and bound-to-miniband (BTM) intersubband transitions with wavelengths coverin...

Two normalized parameters (i.e., s=λ/g and h=a/g, where g is the grating period and a is the width of metal dot) are introduced to characterize the two‐dimensional (2D) double periodic reflection metal grating coupler for a multiquantum well infrared photodetector (QWIP). The ‘‘method of moments’’ is used to analyze this square metal grating struct...

A normal‐incidence type‐II indirect AlAs/Al 0.5 Ga 0.5 As quantum‐well infrared photodetector grown on (110) GaAs by molecular‐beam epitaxy for mid‐ and long‐wavelength multispectrum detection has been developed. The normal‐incident excitation of long‐wavelength intersubband transition was achieved in the [110] X‐band‐confined AlAs quantum wells. S...

Based on the small-signal model of bulk MOSFETs, a counterpart equivalent circuit model for the fully depleted SOI MOSFET is developed by emphasizing the structural uniqueness of the device. Under quasistatic operation conditions, the model parameters valid for all regions of operation, including weak and moderate inversion, are derived and compute...

High‐quality AlGaAs and AlGaAs/GaAs heterostructures have been successfully grown on (110) GaAs at high temperatures by molecular‐beam epitaxy (MBE). Al 0.25 Ga 0.75 As/GaAs high electron mobility transistors with an 18 nm spacer layer yielded 77 K Hall electron mobilities of 6.2×10⁴ and 5.6×10⁴ cm²/V s with sheet c...

An analytic model for fully-depleted silicon-on-insulator (SOI) MOSFETs is derived. In the model, the inversion charge density is related to the front surface potential by the theorems developed for bulk and SOI MOSFETs. The model, which is valid for back surface depletion and accumulation, describes correctly the threshold voltage, the drain curre...

To develop ultra-low dark current and high detectivity planar metal grating coupled bound-to-miniband (BTM) III-V quantum well infrared photodetectors (QWIP's) for 8 to 12 micron focal plane arrays (FPA's) staring IR sensor systems. To develop novel type-I and type II III-V QWIP's with multicolor, broad and narrow band spectral response in the 8 to...

A new photoconductive (PC) and photovoltaic (PV) dual‐mode operation quantum well infrared photodetector using a lattice‐matched n‐type In 0.52 Al 0.48 As/In 0.53 Ga 0.47 As system has been developed for both the narrow‐band (Δλ/λ p =7%) and broadband (Δλ/λ p =24%) detection with a peak spectral response around λ p =10 μm. The detection scheme util...

A new photoconductive (PC) and photovoltaic (PV) dual‐mode operation quantum well infrared photodetection (DM‐QWIP) using an enlarged GaAs (110 Å) quantum well and enlarged Al 0.25 Ga 0.75 As (875 Å) barrier layer has been developed for two‐color intersubband detection. The detection scheme uses transitions from the ground‐state and the first excit...

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A contactless dual‐beam optical modulation (DBOM) technique has been applied to measure the film carrier lifetimes in the SIMOX (separation by implantation of oxygen) wafers with different oxygen implant doses, annealing temperatures, and film thicknesses. Film carrier lifetimes ranging from 0.23 to 0.72 μs were observed in these wafers. The DBOM m...

A detailed study of the dependence of coupling quantum efficiency on the grating periodicity of planar metal grating coupled GaAs/AlGaAs quantum well infrared photodetectors has been made in this work. Five different detector samples with grating periodicities of Λ=1.1, 3.2, 5, 7, and 10 μm have been fabricated for the present study. The results sh...

The statistical variation of the threshold voltage induced by random distributed device parameters is examined in both bulk and SOI MOSFETs. Our study reveals that the threshold voltage of thin-film SOI MOSFETs is less sensitive to inherent fluctuations in device parameters. Design considerations in minimizing the statistical threshold voltage vari...

A metal grating coupled step-bound-to-miniband (SBTM) transition multiquantum well long wavelength infrared photodetector (LWIP) using a lightly strained In(subscript 0.07)Ga(subscript 0.93)As quantum well with a short-period Al(subscript 0.4)Ga(subscript 0.6)As -GaAs superlattice barrier structure has been developed. The new structure created a po...

We report here a detailed study of intersubband absorption at 10.7 micrometers between the localized ground state and the global miniband state in an InAlAs/InGaAs multiple quantum well and short-period superlattice (SL) barrier heterostructure. The use of enlarged quantum well and the superlattice reinforced miniband structure has shown a signific...

The high-low-frequency (HLF) transconductance method is applied to determine the interface state density profile in small-geometry thick- and thin-film (fully depleted) MOSFETs formed on single-and multiple-oxygen implanted (SIMOX) Si substrates. By comparing the real part of the measured high-and low-frequency transconductance and using a static d...

A contactless dual-beam optical modulation (DBOM) technique has been applied to measure substrate carrier lifetimes in SIMOX (Separation by IMplantation of OXygen) wafers with different oxygen implant doses, annealing temperatures and film thicknesses. Substrate carrier lifetimes ranging from 5 to 20 μs were observed in these wafers. The DBOM metho...

A novel n+-v-p+-v-n+ AlGaAs/GaAs heterojunction bipolar transistor (HBT) structure exhibiting negative differential conduction characteristics was successfully developed. Two types of device structures using a thin (10 nm) and a thick (100 nm) p+-GaAs base were studied. The current-voltage characteristics in the thin p+-base structure exhibit a new...

The transient capacitance methods have been applied to study the generation lifetimes and the interface state densities in the top Si film and the underlying substrate of a silicon-insulator-silicon (SIS) capacitor structure formed by oxygen implantation. It is shown that the effect of charge coupling between the film and the substrate can be elimi...

A new step‐bound‐to‐miniband (SBTM) transition multiquantum‐well long‐wavelength infrared photodetector (LWIP) using a lightly strained In 0.07 Ga 0.93 As quantum well and a short‐period GaAs/Al 0.4 Ga 0.6 As superlattice barrier structure has been developed. The new structure created a potential ‘step’ in the superlattice barrier to block the unde...

We report for the first time, the intersubband absorption at 10.7 μm between the localized ground state and the global miniband state in an n‐type InAlAs/InGaAs multiple quantum well and short‐period superlattice barrier heterostructure. The use of enlarged quantum well width and the superlattice reinforced miniband structure has shown a significan...

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We report here a new metal grating coupled top illumination, bound‐to‐miniband transition multiple quantum well/superlattice GaAs/AlGaAs long wavelength infrared detector. By using resonant tunneling and coherent transport along the superlattice miniband, at the same time increasing the effective barrier height of the quantum well and reducing the...

A review of the deep-level defects observed in both electron- and proton-irradiated GaAs solar cells is presented. Studies of the effects of periodic and continuouss thermal annealing on the radiation-induced electron and hole traps and the recombination parameters in GaAs solar cells were made for a wide range of electron and proton energies, flue...

We investigate the response of buried oxide layers formed by oxygen implantation to total dose x‐ray irradiation. The characterization is based on C‐V measurements of the buried oxide capacitor and on back‐channel transistor measurements. Reduced charge trapping is found for material implanted with a lower oxygen dose, annealed at higher temperatur...

A novel method of enhancing Schottky barrier height, while reducing the surface‐state density on n‐type In 0.53 Ga 0.47 As surfaces using P 2 S 5 /(NH 4 ) 2 S and (NH 4 ) 2 S x passivation is described in this communication. The current‐voltage and capacitance‐voltage characteristics show that passivated diodes have lower reverse leakage current an...

A new surface passivation using P 2 S 5 /(NH 4 ) 2 S on GaAs Schottky barrier diodes formed by Au and Al contacts was investigated, and the results were compared with those of (NH 4 ) 2 S x ‐ and NH 4 OH/HF‐treated devices. With new surface treatment, the effective barrier heights for both the Al‐ and Au‐GaAs Schottky diodes were found to vary with...

A high quality In 0.53 Ga 0.47 As Schottky barrier diode fabricated by using a thin graded superlattice (SL) of In 0.53 Ga 0.47 As/In 0.52 Al 0.48 As grown by molecular beam epitaxy is reported for the first time in this letter. The effective Schottky barrier heights of ∼0.71 and ∼0.60 eV were obtained for the Au‐ and Cr‐Schottky contacts, respecti...

A new approach for analyzing the bandgap narrowing in the space-charge region of heavily doped silicon MOS capacitors is presented in this paper. Using high-frequency capacitance-voltage (C-V) measurements on the ultra-thin MOS capacitor structure, the bandgap narrowing versus dopant density in the space-charge region was determined by fitting the...

A numerical simulation of the displacement defect density, the damage constants for minority-carrier diffusion lengths and the degradation of short-circuit current Isc, open-circuit voltage Voc and the conversion efficiency eta sub c in a 1-MeV-electron-irradiated Al0.335Ga0.67As p-n junction solar cell under normal and omnidirectional incidence is...

Studies of the grown‐in defects in multi‐epilayer GaAs (with/without a buffer layer) grown by metalorganic chemical vapor deposition under different [AsH3]/[TMGa] ratios, growth temperatures, and growth rates have been made in this letter by the deep level transient spectroscopy method. For samples without a buffer layer, two electron traps with ac...

Deep-level defects in unirradiated, 1-MeV-electron irradiated, and low-energy proton irradiated LPE-grown Al(x)Ga(1-x)As and Ge p-n junction solar cells were characterized in detail using DLTS, C-V, and I-V measurements. Measurement results indicate that both materials possess good radiation resistance and are suitable for use as the top and bottom...

Studies of the effect of low temperature thermal annealing (170 °C) and laser annealing on grown-in defects in LEC grown Zn-doped InP have been made using the DLTS technique. One hole trap with energy of Ev+∅.52 eV and density of 1.8×10∅15 cm−3 was observed in these InP samples. The potential well for this hole trap was determined by comparing the...

Studies of the grown-in deep level defects vs substrate orientation and gas phase stoichiometry in the VPE GaAs grown by a novel Ga/AsCl3/H2 reactor has been made, using DLTS and C-V methods. Density of electron traps vs Ga/As ratio (i.e., 2/1, 3/1, 4/1, 5/1, and 6/1) was determined for epilayers grown on (100), (211A), and (211B) oriented semi-ins...

Studies of the grown-in deep-level defects in the undoped n-AlxGa1-xAs (x = 0.3) and GaAs epitaxial layers prepared by the liquid phase epitaxy (LPE) techniques have been made, using DLTS, I-V and C-V measurements. The effect of 300 °C thermal annealing on the grown-in defects was investigated as a function of annealing time. The results showed tha...