Native Defects in Wurtzite GaN And AlN

1994 ◽  
Vol 339 ◽  
Author(s):  
P. Boguslawski ◽  
E. Briggs ◽  
T. A. White ◽  
M. G. Wensell ◽  
J. Bernholc
Keyword(s):  
Theoretical Study ◽  
Shallow Donor ◽  
Wave Functions ◽  
Quantum Molecular Dynamics ◽  
Native Defects ◽  
Anion Vacancies ◽  
Cation And Anion Vacancies ◽  
Wide Gap ◽  
Type Character ◽  
Formation Energies

AbstractThe results of an extensive theoretical study of native defects in GaN and of vacancies in AlN are presented. We have considered cation and anion vacancies, antisites, and intersti-tials. The computations were carried out using quantum molecular dynamics, in supercells containing 72 atoms. Due to the wide gap of nitrides, the formation energies of defects depend strongly on the position of the Fermi level. The N vacancy in GaN introduces a shallow donor level that may be responsible for the n-type character of as-grown GaN.Other defects introduce deep states in the gap, with strongly localized wave functions.

scholarly journals Phase-transition–induced p-n junction in single halide perovskite nanowire

2018 ◽  
Vol 115 (36) ◽  
pp. 8889-8894 ◽  
Author(s):  
Qiao Kong ◽  
Woochul Lee ◽  
Minliang Lai ◽  
Connor G. Bischak ◽  
Guoping Gao ◽  
...  
Keyword(s):  
Phase Transition ◽  
Building Blocks ◽  
Chemical Doping ◽  
New Class ◽  
Anion Vacancies ◽  
Cation And Anion Vacancies ◽  
Halide Perovskite ◽  
Two Phases ◽  
P Type ◽  
Formation Energies

Semiconductor p-n junctions are fundamental building blocks for modern optical and electronic devices. The p- and n-type regions are typically created by chemical doping process. Here we show that in the new class of halide perovskite semiconductors, the p-n junctions can be readily induced through a localized thermal-driven phase transition. We demonstrate this p-n junction formation in a single-crystalline halide perovskite CsSnI3 nanowire (NW). This material undergoes a phase transition from a double-chain yellow (Y) phase to an orthorhombic black (B) phase. The formation energies of the cation and anion vacancies in these two phases are significantly different, which leads to n- and p- type electrical characteristics for Y and B phases, respectively. Interface formation between these two phases and directional interface propagation within a single NW are directly observed under cathodoluminescence (CL) microscopy. Current rectification is demonstrated for the p-n junction formed with this localized thermal-driven phase transition.

Void-Lattice Formation in Natural Fluorite by Electron Irradiation

1976 ◽  
Vol 34 ◽  
pp. 614-615 ◽  
Author(s):  
L.E. Murr
Keyword(s):  
Electron Microscope ◽  
Electron Irradiation ◽  
Heavy Ion ◽  
High Energy ◽  
Stoichiometric Ratio ◽  
Direct Observations ◽  
Transmission Electron ◽  
Anion Vacancies ◽  
Cation And Anion Vacancies ◽  
Lattice Formation

The production of void lattices in metals as a result of displacement damage associated with high energy and heavy ion bombardment is now well documented. More recently, Murr has shown that a void lattice can be developed in natural (colored) fluorites observed in the transmission electron microscope. These were the first observations of a void lattice in an irradiated nonmetal, and the first, direct observations of color-center aggregates. Clinard, et al. have also recently observed a void lattice (described as a high density of aligned "pores") in neutron irradiated Al2O3 and Y2O3. In this latter work, itwas pointed out that in order that a cavity be formed,a near-stoichiometric ratio of cation and anion vacancies must aggregate. It was reasoned that two other alternatives to explain the pores were cation metal colloids and highpressure anion gas bubbles.Evans has proposed that void lattices result from the presence of a pre-existing impurity lattice, and predicted that the formation of a void lattice should restrict swelling in irradiated materials because it represents a state of saturation.

Formation Energies and Electronic Structures of Native Defects in GaN

1996 ◽  
Vol 13 (11) ◽  
pp. 867-869 ◽  
Author(s):  
Jian-jun Xie ◽  
Kai-ming Zhang ◽  
Xi-de Xie
Keyword(s):  
Electronic Structures ◽  
Native Defects ◽  
Formation Energies

Formation energies, abundances, and the electronic structure of native defects in cubic SiC

1988 ◽  
Vol 38 (17) ◽  
pp. 12752-12755 ◽  
Author(s):  
C. Wang ◽  
J. Bernholc ◽  
R. F. Davis
Keyword(s):  
Electronic Structure ◽  
Native Defects ◽  
Formation Energies

Theory of Ga, N and H terminated GaN (0001)/(0001) surfaces

1997 ◽  
Vol 482 ◽  
Author(s):  
J. Eisner ◽  
M. Haugk ◽  
R. Gutierrez ◽  
Th. Frauenheim
Keyword(s):  
Electrical Properties ◽  
Theoretical Study ◽  
Growth Conditions ◽  
Mbe Growth ◽  
Atomic Structures ◽  
Mocvd Growth ◽  
Formation Energies

AbstractWe present a theoretical study of atomic structures, electrical properties and formation energies for a variety of possible reconstructions with 1×1 and 2×2 periodicity of the GaN(0001) and (0001) surfaces. We find that during MBE growth in the (0001) direction 2×2 structures become stable under N rich growth conditions while Ga rich environment should yield structures with 1×1 periodicity. Considering MBE growth on (0001) surfaces, among the investigated structures only those with 1×1 periodicity are predicted to be stable. During MOCVD growth, where H terminated surfaces may occur, only structures with lx1 periodicity are found to be stable for both growth directions.

Modeling of Chlorine Related Defects and Complexes in ZnMgSe

2001 ◽  
Vol 677 ◽  
Author(s):  
Yaxiang Yang ◽  
Leonid Muratov ◽  
Bernard R. Cooper ◽  
Thomas H. Myers ◽  
John M. Wills
Keyword(s):  
Ab Initio ◽  
Band Gap ◽  
Electron Concentration ◽  
Defect Complex ◽  
Strong Tendency ◽  
Full Potential ◽  
Native Defects ◽  
Lmto Method ◽  
Formation Energies

ABSTRACTWe have used the ab-initio full potential LMTO method to model native defects and chlorine-impurity-related defects in ZnSe and ZnxMg1−xSe. Our results show that there is a strong tendency for formation of a defect complex between a chlorine impurity at the Se site and a vacancy at the neighboring Zn site. The formation energies of this complex and other chlorine related defects decrease in the presence of magnesium. However, the maximum achievable electron concentration in the presence of magnesium is lower because of the increase in the band gap.

Quantum scar and breakdown of universality in graphene: A theoretical insight

2017 ◽  
Vol 31 (32) ◽  
pp. 1750257
Author(s):  
Kombiah Iyakutti ◽  
Ratnavelu Rajeswarapalanichamy ◽  
Velappa Jayaraman Surya ◽  
Yoshiyuki Kawazoe
Keyword(s):  
Theoretical Study ◽  
New Physics ◽  
Wave Functions ◽  
Dirac Fermions ◽  
Mass Ratio ◽  
Radial Part ◽  
Radial Wave ◽  
Graphene Quantum Dot ◽  
Dirac Equations ◽  
Theoretical Insight

Graphene has brought forward a lot of new physics. One of them is the emergence of massless Dirac fermions in addition to the electrons and these features are new to physics. In this theoretical study, the signatures for quantum scar and the breakdown of universality in graphene are investigated with reference to the presence of these two types of fermions. Taking the graphene quantum dot (QD) potential as the confining potential, the radial part of Dirac equations are solved numerically. Concentrations of the two component eigen-wavefunctions about classical periodic orbits emerge as the signatures for the quantum scar. The sudden variations, in the ratio of the radial wave-functions (large and small components), R(g/f), with mass ratio [Formula: see text] are the signatures for breakdown of universality in graphene. The breakdown of universality occurs for the states k = −1 and k = 1, and the state k = −1 is more susceptible to the breakdown of universality.

Sign in / Sign up

Export Citation Format

Share Document