Transmission electron microscopy of extended crystal defects in proton bombarded and annealed gaas

Abstract

The technique of cross-sectional transmission electron microscopy (TEM) has been applied to study the nature of extended defects in proton bombarded GaAs as a function of dose and post-bombardment anneal. For low doses (up to 5 × 10¹⁵ protons cm⁻²) the main defects were found to be Frank dislocation loops which develop after an anneal at 500°C. In high dose (10¹⁷ protons cm⁻²) samples damage of a diffuse structure was detectable by TEM without annealing. Upon annealing, dislocation networks interspersed with voids became visible. Models for the growth of voids and Frank loops with temperature of anneal have been developed and the experimental details analysed accordingly. From these analyses an average enthalpy for vacancy migration of 0.3 eV is deduced for GaAs.