Abstract
The influence of Al 0.05 Ga 0.95 N cap thickness and growth temperature on the electrical properties of the Al 0.05 Ga 0.95 N/GaN two-dimensional electron gas (2DEG) was investigated. Varying the thickness of the Al 0.05 N barrier led to regions in which the dominant 2DEG scattering mechanisms were either Coulombic or interface roughness/alloy disorder scattering. The 2DEG sheet carrier concentration was found to increase with Al 0.05 Ga 0.95 N cap thickness and saturated at ∼25 nm. By increasing the growth temperature from 650°C to 750°C, the measured low temperature 2DEG sheet carrier concentration was found to decrease and the measured low temperature mobility was found to increase while the Al composition remained constant. Temperature dependent Hall measurements revealed that by increasing the growth temperature, the incorporation of impurities is decreased. A maximum 77 K mobility of ∼19,000 cm 2 /Vs was observed for films grown at 750°C with 20 nm thick Al 0.05 Ga 0.95 N caps.