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Moscow, Russia

Belogorokhov A.,Institute of Rare Metals | Belogorokhova L.,Moscow State University | Gavrilov S.,Moscow Institute of Electronic Engineering
Physica Status Solidi (B) Basic Research

Optical phonons confined in highly monodisperse and nearly spherical ZnSe quasi-zero-dimensionals (QDs) produced in the form of a colloidal solution in porous matrix have been studied experimentally and theoretically. Far-infrared transmission spectra and Raman spectra show a broad band between the bulk transverse optical (TO) and longitudinal optical (LO) phonon frequencies. The data are discussed by calculating the frequencies of the spatially quantized phonon modes in the framework of a continuum model. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Pearton S.J.,University of Florida | Deist R.,University of Florida | Ren F.,University of Florida | Liu L.,University of Florida | And 2 more authors.
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films

A review of the effects of proton, neutron, γ-ray, and electron irradiation on GaN materials and devices is presented. Neutron irradiation tends to create disordered regions in the GaN, while the damage from the other forms of radiation is more typically point defects. In all cases, the damaged region contains carrier traps that reduce the mobility and conductivity of the GaN and at high enough doses, a significant degradation of device performance. GaN is several orders of magnitude more resistant to radiation damage than GaAs of similar doping concentrations. In terms of heterostructures, preliminary data suggests that the radiation hardness decreases in the order AlN/GaN > AlGaN/GaN > InAlN/GaN, consistent with the average bond strengths in the Al-based materials. © 2013 American Vacuum Society. Source

Polyakov A.Y.,Institute of Rare Metals
Springer Series in Materials Science

A review of electron, proton, and neutron damage in GaN and AlGaN is presented. A comparison of theoretical and experimental threshold displacement energies is given, along with a summary of energy levels introduced by different forms of radiation, carrier removal rates and role of existing defects. © Springer-Verlag Berlin Heidelberg 2012. Source

Polyakov A.Y.,Institute of Rare Metals | Pearton S.J.,University of Florida | Frenzer P.,University of Florida | Ren F.,University of Florida | And 2 more authors.
Journal of Materials Chemistry C

This article reviews the effects of radiation damage on GaN materials and devices such as light-emitting diodes and high electron mobility transistors. Protons, electrons and gamma rays typically produce point defects in GaN, in contrast to neutron damage which is dominated by more extended disordered regions. Regardless of the type of radiation, the electrical conductivity of the GaN is reduced through the introduction of trap states with thermal ionization energies deep in the forbidden bandgap. An important practical parameter is the carrier removal rate for each type of radiation since this determines the dose at which device degradation will occur. Many studies have shown that GaN is several orders of magnitude more resistant to radiation damage than GaAs, i.e. it can withstand radiation doses of at least two orders of magnitude higher than those degrading GaAs with a similar doping level. Many issues still have to be addressed. Among them are the strong asymmetry in carrier removal rates in n- and p-type GaN and interaction of radiation defects with Mg acceptors and the poor understanding of interaction of radiation defects in doped nitrides with the dislocations always present. This journal is © The Royal Society of Chemistry 2013. Source

Pearton S.J.,University of Florida | Polyakov A.Y.,Institute of Rare Metals
Chemical Vapor Deposition

Hydrogen is an important component of the gas-phase growth chemistry for GaN, which is typically based on NH3 and (CH3) 3Ga, and also the processing environment for subsequent device fabrication (e.g., SiH4 for dielectric deposition, NH3 or H2 annealing ambients), and is found to readily permeate heteroepitaxial material at temperatures âcircdeg C. Its main effect has been the passivation of Mg acceptors in p-GaN through the formation of neutral Mg-H complexes, which can be dissociated through minority-carrier (electron) injection or simple thermal annealing. Atomic hydrogen is also found to passivate a variety of other species in GaN, as detected by a change in the electrical or optical properties of the material. The injection of hydrogen during a large variety of device fabrication steps has been detected by secondary ion mass sprectrometry (SIMS) profiling using bsupesup H isotopic labeling. Basically all of the acceptor species in GaN, i.e., Mg, C, Ca, and Cd, are found to form complexes with hydrogen. Hydrogen plays an important role in the CVD growth of the wide bandgap GaN and AlGaN materials system and also in the subsequent processing of these semiconductors. It diffuses rapidly in these materials even at quite low temperatures and can profoundly affect the electrical properties. A review is given of the present understanding of hydrogen in the wide bandgap nitrides. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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