NEW MBE BUFFER USED TO ELIMINATE BACKGATING IN GAAS MESFETS.

Backgating from adjacent contact pads is a major source of crosstalk plaguing GaAs MESFET integrated circuits. The backgating is primarily caused by conduction in the buffer layer between the n-GaAs layer and the substrate. In circuits containing LEDs or lasers, crosstalk can also be caused through optical excitation. A buffer layer which is electrically insulating ( rho greater than 10**1**7 OMEGA -cm), completely optically inactive, and on which high-quality GaAs can be grown, has been grown by molecular-beam epitaxy (MBE). This layer, used in GaAs MESFET circuits, was found to eliminate both electrical and optical crosstalk and to improve device breakdown voltages significantly.