Optical studies of Be-implanted GaAs

Abstract

Infrared reflection and transmission measurements of Be‐implanted GaAs have been made as functions of Be‐ion fluence and annealing temperatures from 500 to 800 °C. Semi‐insulating material was implanted with 280‐keV ions with fluences of 1×10¹⁵, 3×10¹⁵, 6×10¹⁵, and 10×10¹⁵ ions/cm². Hole carrier concentrations calculated from the optical measurements as functions of fluence and annealing temperature compare favorably with those determined from sheet Hall‐effect data. The absorption cross section used was obtained from measurements of acceptor‐doped GaAs with concentrations similar to those of the implanted and annealed samples. After annealing at 500 °C a free‐hole plasma layer contribution to the electric susceptibility was observed by measurements of reflection interference effects. Except for the highest‐fluence case the disorder effect on the dielectric constant was largely removed by this anneal. For the highest‐fluence case the annealing results were more complicated. There are regions which still have significantly different optical properties due to residual disorder. The present results are consistent with redistribution effects produced by thermal aging at the higher temperatures.