Reduction of backgating in GaAs/AlGaAs MESFETs by optimisation of active-layer/buffer-layer interface

Backgating measurements made on GaAs MESFETs with abrupt, graded alloy and graded superlattice interface AlGaAs buffer layers were compared to measurements made on conventional GaAs buffer-layer MESFETs. Only the superlattice interface structure showed a reduction in the backgating transconductance (by a factor of 24 compared to the GaAs buffer-layer FET). The lack of reduction in the backgating transconductance for the abrupt and graded alloy interface devices is attributed to traps resulting from GaAs growth on an AlGaAs layer.