Controllable nitrogen doping of MOCVD Ga₂O₃ using NH₃

We report on the controllable nitrogen doping of beta-Ga2O3 as a deep acceptor dopant using ammonia diluted in nitrogen (NH3/N-2) as a source of active nitrogen in the metal organic chemical vapor deposition epitaxy. The effects of the NH3/N-2 flow rate and substrate temperature on the incorporation efficiency, reproducibility, and controllability of N doping into Ga2O3 were studied using secondary ion mass spectrometry measurements. With the increase in the NH3/N-2 molar flow rate from similar to 2 x 10(-8) to similar to 2 x 10(-6) mol/min, the N impurities incorporated into the b-Ga2O3 increased linearly from similar to 1 x 10(18) to similar to 2 x 10(20) cm(-3). At low substrate temperatures (<800 degrees C), hydrogen was incorporated into the film accompanying nitrogen with comparable concentrations. Despite this, the current-voltage measurements showed that the N and H co-doped films were resistive with a measured resistance of >70 Omega X for a film grown with [N] approximate to [H] of similar to 8 x 10(18) cm(-3). X-ray on-axis (020) and off-axis (111) rocking curve omega-scans and atomic force microscopy measurements show no influence of NH3/N-2 dopant on the structural and surface quality of the films. However, the presence of H promoted the growth of (110) and ((1) over bar 10) facets elongated along the [001] direction. At high growth temperatures (>= 950 degrees C), the H concentration in the films was reduced by nearly similar to 10x, but with a slight increase in the concentration of N. The results show that controllable and repeatable nitrogen doping into beta-Ga2O3 can be achieved using ammonia to obtain deep acceptor doping or compensation needed for device engineering in beta-Ga2O3-based power electronic devices.