CONTROL OF SULFUR DOPING FOR GaAs VPE LAYERS.

It has been found that the deposition of GaAs on a (111)A, (111)B, (110), or (100) oriented single crystal placed just above the substrate reduces incorporation of sulfur into GaAs VPE layers on (100) oriented substrates. Sulfur incorporation is reduced by about two orders of magnitude when the (111)A GaAs is placed just above the substrate. A technique for controlling sulfur doping into GaAs VPE layers was developed utilizing this effect. GaAs VPE layers with an extremely abrupt doping profile can be obtained for MESFET applications by using this technique. This technique also permits the growth of VPE layers with a doping profile for Lo-Hi-Lo GaAs IMPATT's with an improved conversion efficiency.