Defect reaction network in C-doped GaAs : numerical predictions.

Abstract

This Report characterizes the defect reaction network in carbon doped, p-type GaAs deduced from first principles density functional theory. The reaction network is deduced by following exothermic defect reactions starting with the initially mobile interstitial defects reacting with common displacement damage defects in C-doped GaAs until culminating in immobile reaction products. The defect reactions and reaction energies are tabulated, along with the properties of all the carbon-related defects in the reaction network. This Report serves to extend the results for intrinsic defects in: P.A. Schultz and O.A. von Lilienfeld, "Simple intrinsic defects in GaAs", Modelling Simul. Mater. Sci Eng., Vol. 17, 084007 (2009)

Transport-reaction model for defect and carrier behavior within displacement cascades in gallium arsenide

“…The selection of defect species and reactions included in the model is guided by calculations of defect properties in GaAs using density functional theory [12][13][14][15][16][17]. Marlowe and molecular dynamics simulations show that the defects produced in the initial collision cascade include primarily interstitials, vacancies and anti-site defects on the Ga and As sublattices, plus divacancies and di anti-site defects [18].…”

“…The process is implemented in the model as an additive term to the diffusion coefficients of As I (+1) and As I (0), using equation (36) with the frequencies ν equal to the carrier capture rate per defect ν=σ v th n, and the hop distance d equal to the lattice constant times a scale factor with nominal value of 1. Here σ, v th , and n are the capture cross section, thermal velocity and concentration for electrons or holes as used in the reaction equations (14)(15)(16)(17)(18)(19)(20). Thus, As I (+1) makes one hop for each electron capture and As I (0) makes one hop for each hole capture.…”

“…Mobile interstitials can react with immobile defects and dopants. Charge states and formation energies of the various reacting and product species, and hence the reaction enthalpies, were determined by DFT using the Gaussian basis code SeqQuest [13][14][15]. Table 3 Table 3 includes corresponding reactions with generic immobile species.…”

“…Reactions in which a defect captures or emits a carrier are of the form illustrated below for the electron capture/emission reaction e + Z Q  Z Q-1 + ΔE e (Z Q-1 ); (14) in the forward or exothermic direction, a conduction electron is captured by a defect of type Z in charge state Q, while in the inverse reaction an electron is emitted from a defect of type Z in charge state Q-1. ΔE e (Z Q-1 ) is the positive difference in energy between the initial and final states, also equal to the energy to emit an electron from defect Z Q-1 to the conduction band.…”

Defect reaction network in Si-doped GaAs : numerical predictions.

“…All reactions of the three potentially mobile species, the arsenic and gallium selfinterstitials and the silicon interstitials, with the common immobile defects, the vacancies and dopants are considered. The reaction energies among intrinsic defects are summarized in a companion report on the carbon reaction network [15]. The results for charge conserving reaction for the remaining silicon-containing reactions are presented in the following Table.…”