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The features of eight-period In0.2Ga0.8N/GaN quantum wells (QWs) with silicon (Si) doping in the first two to five quantum barriers (QBs) in the growth sequence of blue light-emitting diodes (LEDs) are explored. Epilayers of QWs’ structures are grown on 20 pairs of In0.02Ga0.98N/GaN superlattice acting as strain relief layers (SRLs) on patterned sa...
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Citations
... This S-shaped behavior is given with a band-tail model. The fitting parameters of the band-tail model are determined by fitting Eq. (4) to experimental S-shape data, as shown in [21,67]. It seems that the localized states remain approximately the same in sample A with 2-QWs and sample C with 4-QWs. ...
The photoluminescence (PL) properties of InGaN/GaN multiple quantum wells (MQWs) samples with a different quantum well number (two, three, and four) grown by molecular beam epitaxy have been studied in the temperature range between 3 and 300 K. The redshift-blueshift-redshift in the PL peak energy of InGaN well, which is known that as S-shaped behavior, is observed with increasing temperature in the investigated samples. S-shaped behavior is associated with carrier localization states and inhomogeneity in InGaN/GaN MQWs samples. This behavior is explained with the theoretical band tail model. The parameters showing the effect of carrier localization degree are determined and discussed in detail. Furthermore, it is presented the activation energy of charge carriers by using InGaN related-normalized PL peak intensity as a function of the reverse of temperature and Arrhenius function for all samples. The highest PL intensity is obtained in sample B with 3-QWs. Determining carrier localization effect and activation energy plays a vital role in luminescence efficiency and quality of InGaN/GaN MQWs devices.
... In these cases, additional tensile stress from Si doping will be brought in. In recent years, efforts have been made to overcome these difficulties via using intermediate layers with suitable compressive stress to counterbalance tensile stress [10][11][12][13][14][15][16], delta doping for strain relaxation [17,18], or the lattice-matched buffer layer deposition [19,20]. According to previous works [17], periodic Si δ-doping architecture of the n-type GaN layer could achieve smoother GaN layer with higher crystalline quality and lower crack density than on Si uniformly doped GaN. ...
This paper reports the photoluminescence (PL) properties of InGaN/GaN multiple quantum well (MQW) light-emitting diodes grown on silicon substrates which were designed with different tensile stress controlling architecture like periodic Si δ-doping to the n-type GaN layer or inserting InGaN/AlGaN layer for investigating the strain-controlled recombination mechanism in the system. PL results turned out that tensile stress released samples had better PL performances as their external quantum efficiencies increased to 17%, 7 times larger than the one of regular sample. Detail analysis confirmed they had smaller nonradiative recombination rates ((2.5~2.8)×10-2 s-1 compared to (3.6~4.7)× 10-2 s-1), which was associated with the better crystalline quality and absence of dislocations or cracks. Furthermore, their radiative recombination rates were found more stable and were much higher ((5.7~5.8) ×10-3 s-1 compared to [9~7] ×10-4 s-1) at room temperature. This was ascribed to the suppression of shallow localized states on MQW interfaces, leaving the deep radiative localization centers inside InGaN layers dominating the radiative recombination.
... As direct wide band gap semiconductors, GaN and related compounds have achieved great success in lightemitting diodes [1][2][3], laser diodes [4], and highelectron-mobility transistors [5,6]. The heteroepitaxy of GaN film on sapphire, silicon carbide, or single crystal silicon, however, induces a high density of dislocation. ...
Structure shift of GaN nanowall network, nanocolumn, and compact film were successfully obtained on Si (111) by plasma-assisted molecular beam epitaxy (MBE). As is expected, growth of the GaN nanocolumns was observed in N-rich condition on bare Si, and the growth shifted to compact film when the Ga flux was improved. Interestingly, if an aluminum (Al) pre-deposition for 40 s was carried out prior to the GaN growth, GaN grows in the form of the nanowall network. Results show that the pre-deposited Al exits in the form of droplets with typical diameter and height of ~ 80 and ~ 6.7 nm, respectively. A growth model for the nanowall network is proposed and the growth mechanism is discussed. GaN grows in the area without Al droplets while the growth above Al droplets is hindered, resulting in the formation of continuous GaN nanowall network that removes the obstacles of nano-device fabrication.
Visible light communication (VLC) is an important complementary technology to traditional radio frequency (RF) communication due to the abundance of available frequency resources and the high data rates. VLC systems are, however, constrained by the low
$-$
3 dB bandwidth of light-emitting diodes (LED) and high bit error rates (BER). Herein, we propose a vertical-structure micro-LED array with an Si-doped first quantum barrier (FQB) that suppresses the quantum confinement Stark effect (QCSE), increasing the radiative recombination rate. The micro-LED array exhibits an
$-$
3 dB bandwidth of 578 MHz at 2000 A/cm
$^{\text{2}}$
when the Si doping content of the FQB is
$\text{8}\ttimes\text{10}^\text{18}$
cm
$^{\text{$
-
$3}}$
. A data rate of 1.61 Gb/s with a BER of
$\text{3.51}\ttimes\text{10}^{\text{$
-
$3}}$
over the distance of 1 m free space was demonstrated using the on-off keying (OOK) modulation scheme. This work shows great potential for high-speed VLC systems by proposing a simple way to improve communication performance.
The optoelectronic characteristics of AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) with AlInGaN/AlInN superlattices electron blocking layer (EBL) are numerically investigated. The results show that DUV LED with AlInGaN/AlInN EBL has superior carrier confinement capability over the DUV LED with conventional AlGaN EBL. Hence, the internal quantum efficiency (IQE) and radiative recombination rate of the proposed LED is increased by 49% and 219%, respectively as compared to conventional LED. This is assigned to the optimal recombination of electron-hole pairs in the active zone of the proposed LED. Interestingly, the proposed LED also exhibits near-droop-free efficiency.
