High doping level by rapid thermal annealing of Mg-implanted GaAs/GaAlAs for heterojunction bipolar transistors

Rapid thermal annealing (RTA) of Mg-implanted GaAS/ GaAlAs to contact the base layer of heterojunction bipolar transistors (HBT's) is reported. Annealing cycles with time durations of a few seconds and temperature in the range of 850-950°C have been tested. Electrical properties of the annealed samples have been investigated using an electrochemical measurement technique. It was found that hole concentrations as high as 4 × 1019cm-3and electrical activities up to 70 percent can be obtained when high doses of Mg are implanted. This high doping level is very important since the final objective is to realize a contact region to the p-type base layer of HBT's through a highly doped n+ GaAs contact layer.