Annealing Behavior of Be- and Mg-Implants in GaAs

Abstract

Mg+ and Be+ ions were implanted into semi-insulating GaAs with doses ranging from 1014 to 2·1015 cm-2. Both implants were annealed by furnace anneal (FA) as well as by rapid thermal anneal (RTA) with various annealing temperatures and were analyzed by Secondary Ion Mass Spectroscopy (SIMS), Hall and electrochemical carrier profile measurements. Both Mg and Be as-implanted profiles can be fitted by Pearson-IV distributions. After RTA SIMS measurements show significant diffusion only for high-temperature anneals. In this case Be exhibits large diffusion tails and distinct steps in the atomic profile, whereas Mg shows only a slight dopant redistribution. However, after FA generally strong dopant redistribution and surface peaks can be observed. Mg implants yield lower activation and higher sheet resistances than Be when identical implantation doses and annealing cycles are used.