Abstract
GaAs wafers were prepared by various ingot annealing and wafer annealing techniques. The quality of wafers was evaluated by AB-etching and IR tomography. MESFET's with a repeat distance of 10-mu-m were also fabricated on these wafers and the microscopic threshold voltage variations were evaluated. It was found that the threshold voltage variations were from 10 mV to 25 mV for ingot annealing and from 8 mV to 14 mV for multiple wafer annealing (MWA), respectively. Examination by AB-etching and IR tomography also showed that MWA wafers had better uniformities.