AlGaN/GaN high-electron-mobility-transistors on sapphire and silicon carbide substrates were characterized by means of electrical and microcathodoluminescence spectral measurements. Quarter wafer-scale comparisons of spectral features in the GaN attributed to donor–acceptor pair transitions and yellow luminescence from deep acceptors show that the specific contact resistance was related to the ratio of the donor–acceptor pair to yellow luminescence defect emission intensities. This suggested that these defects interact to change the contact resistance locally on the GaN side of the AlGaN/GaN interface. It was shown that changes in the frequency response of these transistors could be attributed to these defects at the interface.

Effects of Deep-Level Defects on Ohmic Contact and Frequency Performance of AlGaN/GaN High Electron-Mobility Transistors. G.H.Jessen, R.C.Fitch, J.K.Gillespie, G.D.Via, B.D.White, S.T.Bradley, D.E.Walker, L.J.Brillson: Applied Physics Letters, 2003, 83[3], 485-7