J.F. Zhang

• BEng PhD
• Professor at Liverpool John Moores University

This study explores Sn-doped Ga2O3 thin films synthesized via the double-pulse metalorganic chemical vapor deposition (MOCVD) method, highlighting its unique advantages in improving film microstructure and electrical properties. The results show that the double-pulse Sn-doped technique, through intermittent atomic supply, promotes medium-range orde...

In this Letter, we present enhancement-mode (E-mode) GaN/AlGaN p-channel metal-oxide-semiconductor field effect transistors (MOSFETs) with excellent performance by introduction of polarization induced tunnel junctions to enhance the source/drain (S/D) contacts and lateral current spreading in the access regions. The S/D contact resistance (RC) of 1...

In this Letter, we report on a p-Cr2O3/n-Ga2O3 vertical heterojunction diode (HJD) with a kilovolt-level breakdown voltage (BV). The chromium oxide (Cr2O3) film was deposited via magnetron sputtering, with a controlled thickness of approximately 20 nm and a hole concentration of 1 × 10¹⁶ cm⁻³. High-resolution transmission electron microscopy of the...

High quality ferroelectric Hf0.5Zr0.5O2 films are crucial for next generation nanoelectronics. However, the growth of large-sized stable ferroelectric Hf0.5Zr0.5O2 films is challenging. Here, we demonstrate the synthesis of large-sized stable orthorhombic ferroelectric Hf0.5Zr0.5O2 thin films through the use of a (111)-oriented platinum electrode a...

In this work, the electrical properties of the Ga2O3 Schottky barrier diodes (SBDs) using W/Au as the Schottky metal were investigated. Due to the 450 °C post-anode annealing (PAA), the reduced oxygen vacancy defects on the β-Ga2O3 surface resulted in the improvement in the forward characteristics of the W/Au Ga2O3 Schottky diode, and the breakdown...

Semitransparent perovskite solar cells (PSCs) that possess a high-power conversion efficiency (PCE) and high average visible light transmittance (AVT) can be employed in applications such as photovoltaic windows. In this study, a bifacial modification comprising a buried layer of [4-(3,6-Dimethyl-9H-carbazol-9-yl) butyl] phosphonic acid (Me-4PACz)...

In this work, a 710 GHz GaN Schottky barrier diode (SBD) with high breakdown voltage was proposed and fabricated. The high-frequency SBDs suffer from the trade-off between the frequency (fc) and breakdown voltage (Vbr). We solved this problem with the gradient doping technique, and the fc and Vbr were improved at the same time. For the proposed gra...

Although GaN has successfully epitaxy growth on 4H‐SiC substrate, its kinetics mechanism, and how to control the morphology and polarity of epitaxial GaN have not been revealed yet. Herein, by investigating the epitaxial process of GaN growth on 4H‐SiC substrate, we found that the Si‐TH and C‐MT configurations are stable for Ga‐N co‐adsorption, S n...

Thermal accumulation under high output power densities is one of the most significant challenges for GaN power devices. Diamond, with its ultra-high thermal conductivity, offers great potential for improving heat dissipation in high-power GaN devices. In this study, nanocrystalline diamond (NCD) passivated high-electron mobility transistors (HEMTs)...

One of the significant technological challenges in safeguarding electronic devices pertains to the modulation of electromagnetic (EM) wave jamming and the recycling of defensive shields. The synergistic effect of heterodimensional materials can effectively enable the manipulation of EM waves by altering the nanostructure. Here we propose a novel ap...

In this work, the strong connection between the channel and the barrier layer of AlGaN channel heterostructures has been investigated in detail. Unlike GaN as a channel material, AlGaN channel layers significantly influence the transport characteristics and quality of AlGaN barrier layers with increasing Al composition. Furthermore, the stress mech...

In this work, a high-performance AlGaN-channel Schottky barrier diode with high breakdown voltage of 2.23 kV defined at anode leakage current of 1 μA and high power figure-of-merit of 614 MW/cm² is demonstrated. Anode voltage (VA) with a clear linear relationship as a function of temperature from 300 to 525 K shows great potential for temperature s...

This paper proposes a terminal matching network (TMN) technology, which can realize wideband matching of microwave rectifiers in a wide input power range. At the same time, it is proposed to realize ultra-wideband microwave rectifiers by connecting two TMN branches of different frequencies in parallel. In order to verify this theory, two rectifiers...

Schottky-type p-GaN gate HEMTs with a low forward bias gate breakdown voltage V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G-BD</sub> are vulnerable to failures during switching. In this work, high-performance MIM/p-GaN gate HEMTs with a TiN/Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" x...

With a dense two-dimensional hole gas (2DHG) p-type conductive layer near the surface, hydrogen-terminated (C–H) diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) have shown typical normally-on operations and high breakdown voltages ( V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink...

Semiconducting single-walled carbon nanotubes (SWCNTs) have stimulated tremendous research interest in high performance electronics thanks to their impressive mechanical and electronic properties. However, it is still challenging to prepare wafer-scale SWCNTs thin films and fine-tunable device performance. Here, layer-by-layer (LbL) assembly is pre...

To enhance gate swing and reduce gate leakage in p-GaN gate high electron mobility transistors (HEMTs), this work introduces novel metal-insulator–semiconductor (MIS) p-GaN tunneling gate HEMTs with an ultrathin Al2O3 tunneling layer. By varying the oxygen sources of atomic layer deposition (ALD), as well as the Al2O3 thickness of the MIS structure...

In this letter, an E-Mode GaN-Si(100) monolithic heterogeneous integration cascode switch (RBMHIC-switch) with reverse blocking compatibility on a SiC substrate with an AlN buffer layer is demonstrated. The RBMHIC-switch with L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GD</sub> of 22 μm showed a...

This letter reports the polycrystalline diamond (PCD) dosimeter with near ideal linearity and high sensitivity to meet the application requirements of medical X-ray dose measurement for low cost, large size, and high performance. The device is fabricated by using hydrogen termination modulation ohmic contact and high-quality materials with preferre...

In this work, we propose a p-NiO/n-Ga2O3 hetero-junction (HJ) Schottky barrier diode (SBD) with low turn-on voltage (Von) and high breakdown voltage (BV) with a trench SBD as a control. An investigation of its electrical characteristics is simulated by Sentaurus TCAD. The HJ SBD utilizes a low work-function anode metal to form a top electrode by re...

In this letter, we show that β-Ga<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> 2 </sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> 3 </sub>-on-SiC RF power metal-oxide-semiconductor field-effect transistors (MOSFETs) can achieve a high output powe...

GaN-on-Si high-electron-mobility transistors have emerged as the next generation of high-powered and cost-effective microwave devices; however, the limited thermal conductivity of the Si substrate prevents the realization of their potential. In this paper, a GaN-on-insulator (GNOI) structure is proposed to enhance the heat dissipation ability of a...

In this work, β-Ga2O3 based Schottky barrier diodes (SBDs) with a composite termination structure of the ZnNiO thin alloy films are reported. β-Ga2O3 SBDs with the junction termination extension structure of the wide-bandgap p-type ZnNiO achieve a breakdown voltage (Vbr) of 2040 V and a specific on-resistance Ron,sp of 3.48 mΩ·cm², contributing a p...

In this work, a comprehensive study of Schottky-gated p-channel GaN field-effect transistors (GaN PFETs) with an energy-band modulated AlGaN barrier layer, a variable gate structure, and various densities of holes in the p-GaN layer is demonstrated to optimize electrical performance. The design rules for high-performance Schottky-gated GaN PFETs no...

In this work, we demonstrated a high-performance NiO/ $\beta$ -Ga $_{\text{2}}$ O $_{\text{3}}$ heterojunction photodetector using piranha solution pretreatment technology. After treatment, the NiO/ $\beta$ -Ga $_{\text{2}}$ O $_{\text{3}}$ heterojunction exhibited an excellent electrical performance, including a higher on/off ratio of 1 $\t...

In this study, we investigated the impact of single stress (negative gate bias stress) and combined stress (both negative gate bias stress and drain voltage stress) on the instability of the threshold voltage (VTH) on p-GaN gate HEMT devices during dynamic switching operation. The dynamic VTH shift during pulsed negative gate bias stress was invest...

A novel cooperative regulatory strategy is proposed in this work to optimize the crystallization dynamics of Formamidinium (FA)‐based perovskite materials, which is achieved by meticulously incorporating the organic molecule guanidinium (GA⁺) and the high boiling point organic solvents N‐Methyl‐2‐Pyrrolidone (NMP) into the perovskite precursor solu...

The gate reliability of p-GaN gate high electron mobility transistors (HEMTs) was investigated in this Letter. Compared with conventional p-GaN gate HEMT, the in situ SiN cap-layer on the p-GaN layer can lift up the energy band and form a metal–insulator–semiconductor structure. With the introduction of an in situ SiN cap-layer, the DC electrical c...

Homogeneous and defect-minimized perovskite films are critical for efficient perovskite solar cells (PSCs). Herein, we introduce a small molecule with electron-rich carbonyl and cyano groups in the perovskite films to regulate the crystallization process and passivate defects. The electron-rich carbonyl and cyano groups of the FDP molecules could c...

Single-crystalline AlN templates are a promising substrate choice for GaN power HEMTs, which have, however, seldom been investigated. In this work, high-performance GaN HEMTs on 2-in AlN templates are successfully demonstrated and evaluated. The buffer lateral leakage was significantly suppressed by five orders of magnitude by epitaxially growing a...

Pre-ohmic-annealing (POA) treatment of P-GaN/AlN/AlGaN epitaxy under N 2 atmosphere was demonstrated to effectively achieve good p-type ohmic contact as well as decreased epitaxy sheet resistance. Ohmic contact resistance ( R c ) extracted by transfer length method reduced from 38 to 23 Ω·mm with alleviated contact barrier height from 0.55 to 0.51...

In this paper, it is demonstrated that the AlGaN high electron mobility transistor (HEMT) based on silicon wafer exhibits excellent high-temperature performance. First, the output characteristics show that the ratio of on-resistance (RON) only reaches 1.55 when the working temperature increases from 25 °C to 150 °C. This increase in RON is caused b...

Hardware integration with biological synaptic function is the key to realizing brain‐like computing. Resistive Random Access Memory (RRAM), with a similar structure to biological synapses, are important candidate for the simulation of biological synaptic function. In this work, Ga2O3 film as a functional layer of RRAM is prepared by the solution me...

Reducing the reversal barrier of Al1−xScxN ferroelectric alloy is critical for improving the coercive voltage and power consumption of ferroelectric devices. Here, the synergistic effect of alloy composition and strain is introduced to optimize the ferroelectric properties of Al1−xScxN alloys. Because of the increased Al–N ionic bond character and...

The growth of gradual boron-doped diamond epitaxial layer was achieved by microwave plasma chemical vapor deposition (MPCVD). Secondary ion mass spectrometry (SIMS) results show that the effective doping concentration range is from 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sup> cm <sup xml...

The application of GaN HEMTs on silicon substrates in high-voltage environments is significantly limited due to their complex buffer layer structure and the difficulty in controlling wafer warpage. In this work, we successfully fabricated GaN power HEMTs on 6-inch sapphire substrates using a CMOS-compatible process. A 1.5 µm thin GaN buffer layer w...

In this work, an in situ C-doped GaN layer inserted into the n-GaN region of ultraviolet light-emitting diodes (UV LEDs) is proposed and investigated to mitigate the severe current crowding effect of GaN-based UV LEDs. Since carbon is a common impurity for GaN grown by metal–organic chemical vapor deposition (MOCVD), it plays the role of deep accep...

In this work, we report on achieving enhanced performance NiOx/beta gallium oxide ( $\beta $ -Ga2O3) heterojunction p-n diodes (HJDs) through synergistic interface engineering (SIE), which can greatly improve the electrical characteristics and interface characteristics of HJDs. It is shown that the NiOx surface undergoes morphological improvement...

Flexible electronic device requires a novel micro-supercapacitors (MSCs) energy conversion-storage system based on two-dimensional (2D) materials to solve the problems of stiffness and complexity. Herein, we report a novel catalytic introduction method of graphene with adjustable porosity by high-energy photon beam. The graphene/Ti3C2T x heterostru...

In this work, high-performance negative differential resistance (NDR) characteristics are demonstrated in homoepitaxial AlN/GaN double-barrier resonant tunneling diodes (RTDs). The devices are grown by plasma-assisted molecular beam epitaxy on bulk GaN substrates and exhibit robust and repeatable NDR at room-temperature. High peak current density o...

Efficient p-type doping is essential and challenging for applications of ultra-wide-bandgap AlGaN with a high aluminum content. Although the band-edge-assisted ionization enabled by the superlattice of [0001] origination can reduce the ionization level due to the raised valence band maximum (VBM), the indispensable electric field induced by the spo...

In this letter, CsPbBr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> wafers are obtained through the pressure-induced aggregation of CsPbBr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> powder and further modified through a high-tempera...

In this work, an energy band-modulated self-aligned p-AlGaN/u-GaN MESFET with a tungsten (W) gate is demonstrated. A high ${I}_{\text {ON}}$ / ${I}_{\text {OFF}}$ of $2\times 10^{{7}}$ , a low subthreshold swing (SS) of 90 mV/dec, and an enhancement-mode threshold voltage ( ${V}_{\text {TH}}$ ) of −0.3 V are obtained. Benefiting from the TMAH...

The emerged wurtzite-type (wz) ferroelectric Al 1 − x B x N alloys have drawn increasing attention due to superior ferroelectricity and excellent compatibility with microelectronics. Revealing and controlling the microstructure and ferroelectric origin is vital to design and fabricate stable wz-Al 1 − x B x N alloy with giant ferroelectricity. We f...

Radiation detectors are important device-level characterization tools of the carrier dynamics of diamond as an ultrawide-bandgap semiconductor. Herein, a high-quality single-crystal diamond was grown on a high-temperature and high-pressure diamond substrate through microwave plasma chemical vapor deposition. We achieved the enhancement of microwave...

In this article, wafer-scale gallium nitride (GaN)-Si(100) monolithic integration material was achieved by transfer printing and self-aligned etching technology. A monolithic heterogeneous integration inverter consists of a normally-OFF Si PMOSFET and a normally-OFF GaN nMOS-HEMT was fabricated on the 2-in wafer-scale GaN-Si(100) integration platfo...

In this study, we reported a novel high Al-composition-AlGaN/GaN MISHEMT on Si with in-situ SiNx enhanced ohmic contacts has been demonstrated. The 45-nm gate AlGaN/GaN MISHEMT on Si exhibits a low on-resistance (Ron) of 0.68 Ω·mm, a high drain current (ID) of 2.63 A/mm, a high transconductance (gm) of 700 mS/mm, and a record cut-off frequency (fT)...

Due to the excellent responsivity and high rejection ratio, Ga2O3-based solar-blind ultraviolet photodetectors (PDs) are attracting more and more attention. The excellent material quality ensures great performance of PDs. In this review, we summarize recent advancements in growth methods of β-Ga2O3 bulk and thin films. Based on high-quality substra...

Gallium oxide (Ga2O3) is an emerging ultra‐wide bandgap (UWBG) semiconductor material that has gained significant attention in the field of high voltage and high frequency power electronics. Its noteworthy attributes include a large bandgap (Eg) of 4.8 eV, high theoretical critical breakdown field strength (EC) of 8 MV cm⁻¹, and saturation velocity...

Degradation and trap evolution in NiO/β-Ga2O3 heterojunction pn diodes under on-state electrical stress were investigated in this work using deep-level transient spectroscopy measurements and density functional theory (DFT) calculations. The decrease in turn-on voltage and forward current appears to correlate with an increase in the concentration o...