scholarly journals The Atomic Rearrangement of GaN-Based Multiple Quantum Wells in H2/NH3 Mixed Gas for Improving Structural and Optical Properties

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Yuhao Ben ◽  
Feng Liang ◽  
Degang Zhao ◽  
Jing Yang ◽  
Zongshun Liu ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Multiple Quantum Well ◽  
Multiple Quantum ◽  
Hydrogen Treatment ◽  
Mixed Gas ◽  
Cross Sectional ◽  
Hydrogen Flux ◽  
Luminescence Efficiency ◽  
Rearrangement Process ◽  
Atomic Rearrangement

AbstractIn this work, three GaN-based multiple quantum well (MQW) samples are grown to investigate the growth techniques of high-quality MQWs at low temperature (750 °C). Instead of conventional temperature ramp-up process, H2/NH3 gas mixture was introduced during the interruption after the growth of InGaN well layers. The influence of hydrogen flux was investigated. The cross-sectional images of MQW via transmission electron microscope show that a significant atomic rearrangement process happens during the hydrogen treatment. Both sharp interfaces of MQW and homogeneous indium distribution are achieved when a proper proportion of hydrogen was used. Moreover, the luminescence efficiency is improved strongly due to suppressed non-radiative recombination process and a better homogeneity of MQWs. Such kind of atomic rearrangement process is mainly caused by the larger diffusion rate of gallium and indium adatoms in H2/NH3 mixed gas, which leads to a lower potential barrier energy to achieve thermodynamic steady state. However, when excessive hydrogen flux is introduced, the MQW will be partly damaged, and the luminescence performance will deteriorate.

Scanning Tunneling Microscope-Induced Luminescence Studies of Defects in GaN Layers and Heterostructures

1999 ◽  
Vol 588 ◽  
Author(s):  
S. Evoy ◽  
C. K. Harnett ◽  
S. Keller ◽  
U. K. Mishra ◽  
S. P. DenBaars ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Scanning Tunneling Microscope ◽  
Multiple Quantum Well ◽  
Scanning Tunneling ◽  
Nanometer Scale ◽  
Multiple Quantum ◽  
Proof Of Concept ◽  
Cross Sectional ◽  
Tunneling Microscope ◽  
Nm Range

AbstractWe present the scanning tunneling microscope-induced luminescence (STL) imaging of defects in optoelectronic materials. Resolution is first discussed using cross-sectional images of InGaAs/GaAs quantum dots. Proof of concept is then provided through the nanometer-scale imaging of GaN layers and quantum wells. The expected λ=356±25 nm range dominates the low temperature STL of GaN. Mapping of luminescence shows circular non-emitting areas around threading dislocations. Extent of dark areas suggests a hole diffusion length of Ld=30–55 nm, in agreement with reported values. The expected λ=450±35 nm range dominates the STL from a buried InGaN/GaN multiple quantum well. Imaging reveals 30–100 nm wide smooth fluctuations of luminescence.

scholarly journals Anomalous Temperature Dependence of Photoluminescence Caused by Non-Equilibrium Distributed Carriers in InGaN/(In)GaN Multiple Quantum Wells

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1023
Author(s):  
Yuhao Ben ◽  
Feng Liang ◽  
Degang Zhao ◽  
Xiaowei Wang ◽  
Jing Yang ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Temperature Dependence ◽  
Multiple Quantum Wells ◽  
Multiple Quantum ◽  
Hydrogen Treatment ◽  
Key Factors ◽  
Anomalous Temperature ◽  
Luminescence Efficiency ◽  
Integrated Intensity ◽  
Non Equilibrium

An increase of integrated photoluminescence (PL) intensity has been observed in a GaN-based multiple quantum wells (MQWs) sample. The integrated intensity of TDPL spectra forms an anomalous variation: it decreases from 30 to 100 K, then increases abnormally from 100 to 140 K and decreases again when temperature is beyond 140 K. The increased intensity is attributed to the electrons and holes whose distribution are spatial non-equilibrium distributed participated in the radiative recombination process and the quantum barrier layers are demonstrated to be the source of non-equilibrium distributed carriers. The temperature dependence of this kind of spatial non-equilibrium carriers’ dynamics is very different from that of equilibrium carriers, resulting in the increased emission efficiency which only occurs from 100 to 140 K. Moreover, the luminescence efficiency of MQWs with non-equilibrium carriers is much higher than that without non-equilibrium carriers, indicating the high luminescence efficiency of GaN-based LEDs may be caused by the non-equilibrium distributed carriers. Furthermore, a comparison analysis of MQWs sample with and without hydrogen treatment further demonstrates that the better quantum well is one of the key factors of this anomalous phenomenon.

scholarly journals Luminescent Characteristics of InGaAsP/InP Multiple Quantum Well Structures by Impurity-Free Vacancy Disordering

2001 ◽  
Vol 692 ◽  
Author(s):  
J. Zhao ◽  
X. D. Zhang ◽  
Z. C. Feng ◽  
J. C. Deng ◽  
P. Jin ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Band Gap ◽  
Annealing Temperature ◽  
Multiple Quantum Well ◽  
Blue Shift ◽  
Multiple Quantum ◽  
Quantum Well Structures ◽  
Cladding Layer ◽  
Cap Layer ◽  
Free Vacancy

AbstractInGaAsP/InP multiple quantum wells have been prepared by Impurity-Free Vacancy Disordering (IFVD). The luminescent characteristics was investigated using photoluminescence (PL) and photoreflectance (PR), from which the band gap blue shift was observed. Si3N4, SiO2 and SOG were used for the dielectric layer to create the vacancies. All samples were annealed by rapid thermal anne aling (RTA). The results indicate that the band gap blue shift varies with the dielectric layers and annealing temperature. The SiO2 capping was successfully used with an InGaAs cladding layer to cause larger band tuning effect in the InGaAs/InP MQWs than the Si3N4 capping with an InGaAs cladding layer. On the other hand, samples with the Si3N4-InP cap layer combination also show larger energy shifts than that with SiO2-InP cap layer combination.

scholarly journals Piezoelectric Level Splitting in GaInN/GaN Quantum Wells

1999 ◽  
Vol 4 (S1) ◽  
pp. 357-362
Author(s):  
C. Wetzel ◽  
T. Takeuchi ◽  
H. Amano ◽  
I. Akasaki
Keyword(s):  
Quantum Wells ◽  
Electric Fields ◽  
High Performance ◽  
Stark Effect ◽  
Electronic Band Structure ◽  
Multiple Quantum Well ◽  
Multiple Quantum ◽  
Large Set ◽  
Electronic Band ◽  
Level Splitting

Identification of the electronic band structure in AlInGaN heterostructures is the key issue in high performance light emitter and switching devices. In device-typical GaInN/GaN multiple quantum well samples in a large set of variable composition a clear correspondence of transitions in photo- and electroreflection, as well as photoluminescence is found. The effective band offset across the GaN/GaInN/GaN piezoelectric heterointerface is identified and electric fields from 0.23 - 0.90 MV/cm are directly derived. In the bias voltage dependence a level splitting within the well is observed accompanied by the quantum confined Stark effect. We furthermore find direct correspondence of luminescence bands with reflectance features. This indicates the dominating role of piezoelectric fields in the bandstructure of such typical strained layers.

Optical properties of GaN Photonic Crystal Membrane Nanocavities at Blue Wavelengths

2005 ◽  
Vol 892 ◽  
Author(s):  
Yong-Seok Choi ◽  
Cedrik Meier ◽  
Rajat Sharma ◽  
Kevin Hennessy ◽  
Elaine D. Haberer ◽  
...  
Keyword(s):  
Optical Properties ◽  
Photonic Crystal ◽  
Quantum Wells ◽  
Multiple Quantum Well ◽  
Light Extraction ◽  
Design Parameters ◽  
Multiple Quantum ◽  
Membrane Structures ◽  
High Q ◽  
Q Factors

AbstractWe have investigated the design parameters for high-Q photonic-crystal (PC) bandgap modes in the emission wavelengths of InGaN/GaN multiple quantum wells. We demonstrate experimental schemes to realize 2D triangular-lattice PC membrane structures, which is essential to obtain photonic bandgap (PBG) modes, and the optical properties of L7 membrane nanocavities that consist of seven missing holes in the Γ-K direction. L7 cavities show pronounced resonances with Q factors of 300 to 800 in the PBG as well as the enhancement of light extraction of the broad InGaN/GaN multiple-quantum-well emission by the 2D PBG.

scholarly journals Photo- and cathodoluminescence investigations of piezoelectric GaN/AlGaN quantum wells

2000 ◽  
Vol 639 ◽  
Author(s):  
E.M. Goldys ◽  
M. Godlewski ◽  
M.R. Phillips ◽  
A.A. Toropov
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Electric Fields ◽  
Free Exciton ◽  
Multiple Quantum Well ◽  
Depth Profiling ◽  
Multiple Quantum ◽  
Recombination Mechanism ◽  
Decay Times ◽  
Piezoelectric Fields

ABSTRACTWe have examined multiple quantum well AlGaN/GaN structures with several quantum wells of varying widths. The structures had strain-free quantum wells and strained barriers. Strong piezoelectric fields in these structures led to a large red shift of the PL emission energies and long decay times were also observed. While the peak energies could be modelled using the effective mass approximation, the calculated free exciton radiative lifetimes were much shorter than those observed in experiments, indicating an alternative recombination mechanism, tentatively attributed to localised excitons. Cathodoluminescence depth profiling revealed an unusually small penetration range of electrons suggesting that electron-hole pairs preferentially remain within the multiple quantum well region due to the existing electric fields. Spatial fluctuations of the cathodoluminescence intensity were also observed.

V-Defect and Dislocation Analysis in InGaN Multiple Quantum Wells on Patterned Sapphire Substrate

2018 ◽  
Vol 787 ◽  
pp. 37-41
Author(s):  
Huan You Wang ◽  
Qiao Lai Tan ◽  
Gui Jin
Keyword(s):  
Quantum Wells ◽  
Strain Relaxation ◽  
Chemical Vapor ◽  
Multiple Quantum ◽  
Cross Sectional ◽  
Patterned Sapphire Substrate ◽  
Sapphire Substrates ◽  
Transmission Electron ◽  
Multi Quantum Well ◽  
Patterned Sapphire Substrates

InGaN/GaN multiquantum well (MQW) structures have been grown on cone-shaped patterned sapphire substrates (CPSS) by metalorganic chemical vapor deposition (MOCVD). From the transmission electron microscopy (TEM) results, we found that most of the threading dislocations (TDs) in the trench region of the CPSS were bent by lateral growth mode. Also the staircase-like TDs were observed near the slant region of the cone pattern, they converged at the slope of the cone patterned region by staircase-upward propagation, which seems to effectively prevent TDs from vertical propagation in the trench region. The associated dislocation runs up into the overgrown GaN layer and MQW, and some (a+c) dislocations were shown to decompose inside the multi-quantum well, giving rise to a misfit segment in the c-plane and a V-shape defect. From cross-sectional TEM, we found that all V defects are not always connected with TDs at their bottom, some V defects are generated from the stacking mismatch boundaries induced by stacking faults which are formed within the MQW due to the strain relaxation.

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