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Crystals
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Group-III Nitride Quantum Wells
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Group-III Nitride Quantum Wells

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Materials for Energy Applications".

Deadline for manuscript submissions: closed (30 June 2024) | Viewed by 5739

Special Issue Editor

Prof. Dr. Sławomir P. Łepkowski

E-Mail Website
Guest Editor
Institute of High Pressure Physics, "Unipress", Polish Academy of Sciences, ul. Sokołowska 29/37, 01-142 Warszawa, Poland
Interests: group-III nitride semiconductors; theory of semiconductor nanostructures; K-P method; ab-initio calculations; topological phase transition; topological insulators
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Group-III nitride quantum wells have become one of the most important semiconductor heterostructures since the discovery of GaN-based light-emitting diodes and laser diodes in the 1990s.  Due to the large differences between the direct band gaps of InN, GaN, and AlN, they can emit light in a very wide spectral region from the far infrared to the deep ultraviolet. The technology of InGaN-based and AlGaN-based quantum wells operating in the blue and near-ultraviolet spectral regions is well established and these heterostructures are widely used in the active regions of commercial light emitters. For nitride quantum wells emitting light from the infrared to green spectral region and in the deep ultraviolet, the efficiency of emission is usually poor due to a number of physical and technological problems, such as large strains, strong built-in electric fields, localization of carriers due to alloy fluctuations, generation of a large number of point defects. Overcoming these problems will allow the development of new optoelectronic devices for numerous applications, including micro-displays, laser projectors, water purification systems, and food preservation tools.

This Special Issue focuses on the most recent advances in group-III nitride quantum wells. The potential topics of this Special Issue include the epitaxial growth of indium-rich or aluminum-rich quantum wells, carrier localization in disordered alloys, the strain-related effects, the built-in electric fields in polar and semi-polar wurtzite structures, defects and non-radiative recombination, optical and electrical properties of nitride quantum wells, zinc-blende nitride quantum wells, light-emitting diodes, and laser diodes.

Prof. Dr. Sławomir P. Łepkowski
Guest Editor

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Keywords

  • group-III nitride semiconductors
  • quantum wells
  • epitaxial growth
  • strain-related effects
  • spontaneous and piezoelectric polarizations
  • alloy fluctuations
  • optical and electrical properties
  • defects
  • radiative and nonradiative recombination
  • light-emitting diodes
  • laser diodes
  • ab-initio calculations and modelling

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Published Papers (3 papers)

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Research

14 pages, 4766 KiB  
Article
Investigation into the Effects of Cross-Sectional Shape and Size on the Light-Extraction Efficiency of GaN-Based Blue Nanorod Light-Emitting Diode Structures
by Bohae Lee and Han-Youl Ryu
Crystals 2024, 14(3), 241; https://doi.org/10.3390/cryst14030241 - 29 Feb 2024
Viewed by 1211
Abstract
We investigated the effect of cross-sectional shape and size on the light-extraction efficiency (LEE) of GaN-based blue nanorod light-emitting diode (LED) structures using numerical simulations based on finite-difference time-domain methods. For accurate determination, the LEE and far-field pattern (FFP) were evaluated by averaging [...] Read more.
We investigated the effect of cross-sectional shape and size on the light-extraction efficiency (LEE) of GaN-based blue nanorod light-emitting diode (LED) structures using numerical simulations based on finite-difference time-domain methods. For accurate determination, the LEE and far-field pattern (FFP) were evaluated by averaging them over emission spectra, polarization, and source positions inside the nanorod. The LEE decreased as rod size increased, owing to the nanorods’ increased ratio of cross-sectional area to sidewall area. We compared circular, square, triangular, and hexagonal cross-sectional shapes in this study. To date, nanorod LEDs with circular cross sections have been mainly demonstrated experimentally. However, circular shapes were found to show the lowest LEE, which is attributed to the coupling with whispering-gallery modes. For the total emission of the nanorod, the triangular cross section exhibited the highest LEE. When the angular dependence of the LEE was calculated using the FFP simulation results, the triangular and hexagonal shapes showed relatively high LEEs for direction emission. The simulation results presented in this study are expected to be useful in designing high-efficiency nanorod LED structures with optimum nanorod shape and dimensions. Full article
(This article belongs to the Special Issue Group-III Nitride Quantum Wells)
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21 pages, 3357 KiB  
Article
Phonon Characteristics of Gas-Source Molecular Beam Epitaxy-Grown InAs1−xNx/InP (001) with Identification of Si, Mg and C Impurities in InAs and InN
by Devki N. Talwar, Tzuen-Rong Yang and Hao-Hsiung Lin
Crystals 2023, 13(10), 1508; https://doi.org/10.3390/cryst13101508 - 17 Oct 2023
Viewed by 1717
Abstract
The lattice dynamical properties of dilute InAs1−xNx/InP (001) epilayers (0 ≤ x ≤ 0.03) grown by gas-source molecular beam epitaxy were carefully studied experimentally and theoretically. A high-resolution Brüker IFS 120 v/S spectrometer was employed to measure the room-temperature [...] Read more.
The lattice dynamical properties of dilute InAs1−xNx/InP (001) epilayers (0 ≤ x ≤ 0.03) grown by gas-source molecular beam epitaxy were carefully studied experimentally and theoretically. A high-resolution Brüker IFS 120 v/S spectrometer was employed to measure the room-temperature infrared reflectivity (IRR) spectra at near-normal incidence (θi = 0). The results in the frequency range of 180–500 cm−1 revealed accurate values of the characteristic In-As-like and In-N-like vibrational modes. For InAs1−xNx alloys, a classical “Drude–Lorentz” model was constructed to obtain the dielectric functions ε~ω in the far IR regions by incorporating InAs-like and InN-like transverse optical ωTO modes. Longitudinal optical ωLO phonons were achieved from the imaginary parts of the simulated dielectric loss functions. The theoretical results of IRR spectra for InAs1−xNx/InP (001) epilayers using a multi-layer optics methodology provided a very good agreement with the experimental data. At oblique incidence (θi ≠ 0), our study of s- and p-polarized reflectance (Rs,p(ω)) and transmission (Ts,p(ω)) spectra allowed the simultaneous perception of the ωTO and ωLO phonons of the InAs, InN and InAs0.97N0.03 layers. Based on the average t-matrix Green’s function theory, the results of local vibrational modes for light SiIn+ donors and SiAs−, CAs− acceptors in InAs were found in good agreement with the existing Raman scattering and infrared spectroscopy data. InInN, however, the method predicted an in-band mode for the MgIn− acceptor while projecting an impurity mode of the SiIn+ donor to appear just above the maximum ωmaxInN[≡595 cm−1] phonon frequency region. In InAs1−xNx/InP (001) epifilms, the comparison of reflectivity/transmission spectra with experiments and the predictions of impurity modes for isoelectronic donor and acceptor impurities in InAs and InN can be valuable for appraising the role of defects in other technologically important semiconductors. Full article
(This article belongs to the Special Issue Group-III Nitride Quantum Wells)
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11 pages, 2992 KiB  
Article
Strain-Induced Band Gap Variation in InGaN/GaN Short Period Superlattices
by Polyxeni Chatzopoulou, Isaak G. Vasileiadis, Philomela Komninou, Vassilis Pontikis, Theodoros Karakostas and George P. Dimitrakopulos
Crystals 2023, 13(4), 700; https://doi.org/10.3390/cryst13040700 - 19 Apr 2023
Cited by 3 | Viewed by 1989
Abstract
The use of strained substrates may overcome indium incorporation limits without inducing plastic relaxation in InGaN quantum wells, and this is particularly important for short-period InGaN/GaN superlattices. By incorporating elastic strain into these heterostructures, their optoelectronic behavior is modified. Our study employed density [...] Read more.
The use of strained substrates may overcome indium incorporation limits without inducing plastic relaxation in InGaN quantum wells, and this is particularly important for short-period InGaN/GaN superlattices. By incorporating elastic strain into these heterostructures, their optoelectronic behavior is modified. Our study employed density functional theory calculations to investigate the variation in the band-gap energy of short-period InGaN/GaN superlattices that comprise pseudomorphic quantum wells with a thickness of just one monolayer. Heterostructures with equibiaxially strained GaN barriers were compared with respective ones with relaxed barriers. The findings reveal a reduction of the band gap for lower indium contents, which is attributed to the influence of the highly strained nitrogen sublattice. However, above mid-range indium compositions, the situation is reversed, and the band gap increases with the indium content. This phenomenon is attributed to the reduction of the compressive strain in the quantum wells caused by the tensile strain of the barriers. Our study also considered local indium clustering induced by phase separation as another possible modifier of the band gap. However, unlike the substrate-controlled strain, this was not found to exert a significant influence on the band gap. Overall, this study provides important insights into the behavior of the band-gap energy of strained superlattices toward optimizing the performance of optoelectronic devices based on InGaN/GaN heterostructures. Full article
(This article belongs to the Special Issue Group-III Nitride Quantum Wells)
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