Search query: energy gap InGaN

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abstract: Since heat generation in electronic devices induces the degradation of performance, the understanding of their thermal properties is required. InGaN and AlInN alloys are possibly the key materials for optical devices in green gap and high power transistors. Characteristic properties of local strain, fluctuation of energy gap, carrier dynamics, and so forth due to spatial nonuniformity of alloy composition are now under investigation, while nonuniform thermal conduction remains unclear. In this report we show nonuniform heat or phonon conductance in the nonuniform field of InGaN alloy composition. An In0.16Ga0.84N (110nm) film grown on GaN grown on a sapphire substrate was characterized by micro Raman spectroscopy with controlling spot positions of two color lasers: 325nm for electronic excitation and phonon generation and 532nm for Raman probe. Thermal properties were analyzed by two dimensional mapping of Raman signal by 532 nm line and its energy shift by introducing the 325nm line. It is found that the phonon transport mainly takes place along the region with low GaN mole fraction or low phonon energy, while some of phonons are transported through narrow regions with higher GaN mole fraction. This pump and probe Raman method gives us phonon transport properties in semiconductors.
author_names: Shungo Okamoto

Naomichi Saito

Bei Ma

Kensuke Oki

Ken Morita

Kazuhiro Ohkawa

Yoshihiro Ishitani
title: Local phonon analysis in InGaN film by mapping of Raman peak energy
venue: 2019 Compound Semiconductor Week (CSW)
year: 2019

abstract: We have used high resolution transmission electron microscopy (HRTEM) aberration corrected quantitative scanning transmission electron microscopy (Q STEM) atom probe tomography (APT) and X ray diffraction (XRD) to study the atomic structure of (0001) polar and (11 20) non polar InGaN quantum wells (QWs) This paper provides an overview of the results. Polar (0001) InGaN in QWs is a random alloy, with In replacing Ga randomly. The InGaN QWs have atomic height interface steps, resulting in QW width fluctuations. The electrons are localised at the top QW interface by the built in electric field and the well width fluctuations, with a localisation energy of typically 20meV. The holes are localised near the bottom QW interface, by indium fluctuations in the random alloy, with a localisation energy of typically 60meV. On the other hand, the non polar (11 20) InGaN QWs contain nanometre scale indium rich clusters which we suggest localise the carriers and produce longer wavelength (lower energy) emission than from random alloy non polar InGaN QWs of the same average composition. The reason for the indium rich clusters in non polar (11 20) InGaN QWs is not yet clear, but may be connected to the lower QW growth temperature for the (11 20) InGaN QWs compared to the (0001) polar InGaN QWs.
author_names: Colin J Humphreys

James T Griffiths

Fengzai Tang

Fabrice Oehler

Scott D Findlay

Changlin Zheng

Joanne Etheridge

Tomas L Martin

Paul A J Bagot

Michael P Moody

Danny Sutherland

Phil Dawson

Stefan Schulz

S Zhang

W Fu

Tongtong Zhu

Menno J Kappers

Rachel A Oliver
title: The atomic structure of polar and non polar InGaN quantum wells and the green gap problem.
venue: Ultramicroscopy
year: 2017

abstract: Abstract The activation energy for Mg acceptor in In x Ga 1 x N alloys is investigated. It is found that there are three factors to influence the activation energy for Mg acceptor. One is the stronger dependence of the VBM of In x Ga 1 x N depending on In content than that of the Mg acceptor energy level. The other is the concentration of Mg acceptors. Another is the extending of the valence band tail states into the band gap. In addition, a model based on modifying the effective mass model is developed. It is found that the model can describe the activation energy for Mg acceptor in the Ga rich In x Ga 1 x N alloys well after considering the influence of the valence band tail states.
author_names: Chuanzhen Zhao

Tong Wei

Li-Ying Chen

Sha-Sha Wang

Jun Wang
title: The activation energy for Mg acceptor in the Ga rich InGaN alloys
year: 2017

abstract: One of the key requirements to achieve solar conversion efficiencies greater than 50% is a photovoltaic device with a band gap of 2.4 eV or greater. lnxGa1 xN is one of a few alloys that can meet this key requirement. InGaN with indium compositions varying from 0 to 40% is grown by both metal organic, chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) and studied for suitability in photovoltaic applications. Structural characterization is done using X ray diffraction, while optical properties are measured using photoluminescence and absorption transmission measurements. These material properties are used to design various configurations of solar cells in PC1D. Solar cells are grown and fabricated using methods derived from the III N LED and photodetector technologies. The fabricated solar cells have open circuit voltages around 2.4 V and internal quantum efficiencies as high as 60% Major loss mechanisms in these devices are identified and methods to further improve efficiencies are discussed
author_names: Omkar K Jani

Christiana B Honsberg

Yong Zhi Huang

J -O Song

Ian T Ferguson

Gon Namkoong

Elaissa Trybus

Alan Doolittle

Sarah R Kurtz
title: Design, Growth, Fabrication and Characterization of High Band Gap InGaN/GaN Solar Cells
venue: 2006 IEEE 4th World Conference on Photovoltaic Energy Conference
year: 2006

abstract: Injection current dependences of electroluminescence transition energy in blue InGaN/GaN multiple quantum wells light emitting diodes (LEDs) with different quantum barrier thicknesses under pulsed current conditions have been analyzed taking into account the related effects including deformation caused by lattice strain, quantum confined Stark effects due to polarization field partly screened by carriers, band gap renormalization, Stokes like shift due to compositional fluctuations which are supposed to be random alloy fluctuations in the sub nanometer scale, band filling effect (Burstein Moss shift) and quantum levels in finite triangular wells. The bandgap renormalization and band filling effect occurring at high concentrations oppose one another, however, the renormalization effect dominates in the concentration range studied, since the band filling effect arising from the filling in the tail states in the valence band of quantum wells is much smaller than the case in the bulk materials. In order to c.
author_names: Feng Zhang

Masao Ikeda

Kun Zhou

Zongshun Liu

Jianping Liu

Shu-ming Zhang

Hui Yang
title: Injection current dependences of electroluminescence transition energy in InGaN/GaN multiple quantum wells light emitting diodes under pulsed current conditions
year: 2015

abstract: In this study, non radiative recombination center in InGaN films with varying III/N ratio grown by rf molecular beam epitaxy was investigated directly by piezoelectric photothermal spectroscopy (PPTS) To clarify the influence of the III/N supply ratio during the InGaN layer growth, the nitrogen flow rate was changed from 1.0 to 2.0 sccm. Since metallic indium droplets and phase separation were observed for the samples grown by low nitrogen flow rate, it was found that these have been grown under a group III rich condition. With increasing nitrogen flow rate, the indium content in InGaN films increased. The estimated non radiative recombination edges determined from PPTS method (PPT edge) red shifted with increasing the nitrogen flow rate. The energy difference between estimated band edge and the PPT edges increased with increasing flow rate under group III rich condition, and became saturated under the N rich condition. It is considered that the existence of the phase separation is related to this behavior. (c) 2008 WILEY VCH Verlag GmbH Co. KGaA, Weinheim)
author_names: Hironori Komaki

T Shimohara

Kentaro Sakai

Ryuji Katayama

Kentaro Onabe

Atsuhiko Fukuyama

Tetsuo Ikari
title: Band gap energy fluctuations in InGaN films grown by RF MBE with changing nitrogen supply rate investigated by a piezoelectric photothermal spectroscopy
year: 2008

abstract: We have carried out a theoretical study for calculating the electronic and optical properties of \text{In}}_{x} \text{Ga}}_{1 x} \text{N}\text{GaN} $InxGa1 xN/GaN(001) superlattices with short periodicity, while In composition is altered from 0 to 100 These appealing systems have been simulated using ab initio method in the framework of full potential linearized augmented plane wave scheme. In this respect, a modified Becke Johnson for the exchange and correlation potential term is included for describing adequately the energy gap of these promising low dimensional materials. Exclusively, we computed the density of states, imaginary part of dielectric function, refractive index and absorption coefficient. However, it is viable to control the optical properties of these superlattices which may be useful for optoelectronic devices application.
author_names: Amel Laref

A Altujar

Shi-jun Luo
title: Theoretical study of band gap engineering and optical absorption in InGaN/GaN superlattices with short periodicity
year: 2014

abstract: Optoelectronic systems based on elements of the nitride family, mainly, those based on GaN/InGaN alloys offer huge potentialities in solar cell applications, as example in concentrated photovoltaic (CPV) for the realization of solar photovoltaic cells (SPC) mainly thanks to the large tunability of the band gap related to the ternary In Ga N concentrations in the layers. This paper investigates temperature effects on the electronic and electrical parameters, and thus efficiency of GaN/InGaN SPCs with respect to the N face configuration. In an attempt to determine the energy bands all along with the cell's photovoltaic parameters, a numerical model is proposed. The model considers the indium composition and the host lattice temperature. Moreover, the developed model highlights the polarization effects on the performances of nitride SPCs.
author_names: Rabeb Belghouthi

Michel Aillerie

Amani Rached

H Mejri
title: Effect of temperature on electronic and electrical behavior of InGaN double hetero junction p i n solar cells
venue: Journal of Materials Science: Materials in Electronics
year: 2019

abstract: Abstract. We demonstrate an effective approach to enhancing the performance of III nitride based photoelectrode by utilization of hot electrons generated from localized surface plasmons (LSPs) The device designed as a TiO2 Au InGaN sandwich structure is fabricated by cladding Au nanodroplets with a thin TiO2 layer to provide a large interfacial layer, which is beneficial for the hot electron collection efficiency by electron reflection via an additional energy barrier. The applied bias photo to current efficiency is enhanced by up to four times due to the contribution of hot electrons generated from the absorbed light with wavelengths >470 nm, corresponding to photon energies below the band gap of InGaN (2.67 eV) recognized from incident photon to current efficiency spectrum. The LSPs of our photoelectrodes also exhibit a suppressed size dependence on the metal nanodroplets, feasible for mass production.
author_names: Yaonan Hou
title: Engineering hot electrons of localized surface plasmon on InGaN photoanode for solar powered water splitting
venue: Journal of Photonics for Energy
year: 2019

abstract: Due to their technological application, a precise prediction of the optical properties of III nitride alloys is significantly attractive. Numerical simulation based on first principles calculations is applied to study the structural characteristics and band energy properties of the zincblende Ga1 xInxN. The purpose of this study is to explore theoretically the electronic and optical characteristics of the parent InN and GaN compounds and their ternary alloys by utilizing KKR CPA approach. We show that density functional theory is a very powerful tool for: 1 studying the local doping effects, 2 defects effect, 3 size and disorder effect on optical and electronic properties of these materials, 4 predicting properties of new materials.
author_names: Elmehdi Salmani

Adil Marjaoui

Omar Mounkachi

Monaam Ben Ali

Hassan El Moussaoui

Hamid Ez-Zahraouy

Mohamed Hamedoun

Mohammed Benaissa

Abdelilah Benyoussef
title: Band gap engineering of (InGaN) for photovoltaic application
venue: 2014 International Renewable and Sustainable Energy Conference (IRSEC)
year: 2014