Low-dose n-type implantation into Cr-doped GaAs substrates

Results are presented of low dose n-type implants (Se+) made directly into Cr-doped GaAs which show anomalous results on a large percentage of commercially available ingots due to substrate variations. The variation between different materials may result in a thin n-type skin of 'anomalous excess carriers' in some ingots and a low activation of the implanted ions in others. On the ingots that show 'excess carriers', an improved encapsulation procedure can substantially reduce, if not eliminate, the excess sheet concentration. On the ingots that show low activation, an ion-implantation-damage gettering technique can be used to increase the activation of implanted ions to >= 80%. These procedures, should encourage a wider use of ion implantation directly in Cr-doped semi-insulating GaAs for the fabrication for devices. (U.K.)