Controlled gate surface processing of AlGaN∕GaN high electron mobility transistors

The authors have used ultrahigh vacuum surface science techniques combined with gate mask fabrication and processing to demonstrate improvements in the unity gain cutoff frequency response fT of AlGaN∕GaN high electron mobility transistors compared to standard processing. In situ annealing, nitrogen ion sputtering and annealing, and Ga reflux plus annealing all displayed increased fT response on average. In situ depth-resolved cathodoluminescence spectroscopy of the AlGaN∕GaN interface region reveals changes in GaN near-band edge, 2.2eV, and 2.9eV native defect emissions consistent with the average device performance between process steps and between devices with the same treatment on the same wafer.