Demonstration of controllable Si doping in N-polar AlN using plasma-assisted molecular beam epitaxy

In this study, we present the demonstration of controllable Si doping in N-polar AlN films grown on single-crystal AlN substrates by plasma-assisted molecular beam epitaxy. Through optimization of growth conditions, we obtained high-quality N-polar AlN films at 950 ° C. However, our studies revealed that Si incorporation dramatically decreases at such high growth temperature. To enable higher Si incorporation, a hybrid low-temperature and high-temperature growth condition was developed by using Ga as a surfactant at low-temperature growth. By lowering the growth temperature of AlN to 750 °C, we were able to incorporate Si with concentrations as high as 2 × 10 20 cm − 3 and demonstrated an electron concentration as high as 1.25 × 10 19 c m − 3 at room temperature. The secondary ion mass spectrometry analysis revealed that, < 0.2 % Ga is incorporated in the AlN films grown with Ga as a surfactant at low temperature.