Impact of low growth temperature on hole concentration in polarization-doped AlGaN on AlN

We investigated the impact of growth temperature on hole concentration in polarization-doped AlGaN with high AlN mole fraction on AlN, without Mg doping. A significantly lower growth temperature (around 800 °C) results in a higher hole concentration of 5 × 1018 cm−3 at room temperature in polarization-doped AlGaN without Mg doping, compared with traditional growth temperatures above 1000 °C. Furthermore, a hole concentration of 1 × 1018 cm−3 was observed even at 80 K in such an AlGaN layer without Mg doping, indicating that the hole concentration of 1 × 1018 cm−3 was induced by polarization doping alone. Previously, the hole concentrations in such AlGaN layers relied on a combination of polarization doping and Mg doping. Our results demonstrate that low growth temperature enables high hole concentration even without Mg doping.