Electron irradiation of AlGaN/GaN and AlN/GaN heterojunctions

The effects of 10 MeV electron irradiation on AlGaN/GaN and AlN/GaN heterojunctions grown by molecular beam epitaxy are reported. The irradiation increases the resistivity of the GaN buffer due to compensation by radiation defects with levels near Ec-1 eV and decreases the mobility of the two-dimensional electron gas (2DEG) near the AlGaN/GaN (or AlN/GaN) interface. The bulk carrier removal rate in the GaN buffer is the same for both types of structures and similar to carrier removal rates for undoped n-GaN films. In structures with a density of residual donors of ∼1015 cm-3, irradiation with electron doses of ∼5x1015 cm-2 renders the buffer semi-insulating. The 50% degradation of the 2DEG conductivity happens at several times higher doses (close to 3x1016 cm-2 versus 6.5x1015 cm-2) for AlN/GaN than for AlGaN/GaN structures, most likely because of the lower thickness of the AlN barrier