Model for transport and reaction of defects and carriers within displacement cascades in gallium arsenide

Abstract

A model is presented for recombination of charge carriers at evolving displacement damage in gallium arsenide, which includes clustering of the defects in atomic displacement cascades produced by neutron or ion irradiation. The carrier recombination model is based on an atomistic description of capture and emission of carriers by the defects with time evolution resulting from the migration and reaction of the defects. The physics and equations on which the model is based are presented, along with the details of the numerical methods used for their solution. The model uses a continuum description of diffusion, field-drift and reaction of carriers, and defects within a representative spherically symmetric cluster of defects. The initial radial defect profiles within the cluster were determined through pair-correlation-function analysis of the spatial distribution of defects obtained from the binary-collision code MARLOWE, using recoil energies for fission neutrons. Properties of the defects are discussed and values for their parameters are given, many of which were obtained from density functional theory. The model provides a basis for predicting the transient response of III-V heterojunction bipolar transistors to displacement damage from energetic particle irradiation.

Migration processes of the As interstitial in GaAs

“…Modeling device performance following radiation damage requires quantitative information about the defect populations and their charge states, levels, and migration processes. 1,2 Migration processes of highly mobile defects are especially important because they can dominate the annealing of the radiation damage, and thus, control the rate at which the device performance recovers. Experimental studies of radiation damage and annealing in GaAs devices suggest that the As interstitial (I As ) may be such a defect.…”

First-principles survey of the structure, formation energies, and transition levels of As-interstitial defects in InGaAs

“…Our interest in defect transport immediately following radiation-damage events produces a focus on highly non-equilibrium defect populations, with the effect of alloying on such populations taking on particular importance. Within this context, the importance of As interstitials stems from their reputation as the most mobile of the intrinsic defects in GaAs, which causes them to dominate defect transport at short time scales following displacement-induced radiation-damage events [12,13]. A similar importance is expected in displacement-damaged devices utilizing InGaAs alloys.…”

“…The reduced variation of the levels arises from the differencing of correlated formation energies for atomically similar defects in adjacent charge states, as needed to obtain the level for each sampled alloy configuration. In closing, we note that the observed dependence of defect properties on the local alloy environment fundamentally alters defectdiffusion pathways in a manner not captured by existing transport models for unalloyed materials [11,12]. Table I.…”

“…These purely statistical parameters do not, however, describe the defect populations expected at thermal equilibrium. At thermal equilibrium in GaAs subject to As-rich conditions, the dominant ground-state defects are the As antisite (in p-type GaAs) and the Ga vacancy (in n-type GaAs), with As-interstitials lying ~2-3 eV higher in formation energy [12,13,17]. Because of the high formation energy of As interstitials relative to other intrinsic defects, the As interstitials will have negligible equilibrium concentrations at room temperature.…”

“…Our long-term goal is to determine a broad set of InGaAs-alloy defect properties, as needed to enable continuum modelling of the transport and reaction of defects created by radiation-induced displacement-damage cascades in InGaAsbased heterojunction bipolar transistors (HBTs). Such models have been extensively pursued for Si and GaAs [11,12], but limited knowledge of defects in alloys hinders extension to InGaAs-based HBTs.…”