Controllable nitrogen doping of MOCVD Ga2O3 using NH3.

We report on the controllable nitrogen doping of β-Ga₂O₃ as a deep acceptor dopant using ammonia diluted in nitrogen (NH₃/N₂) as a source of active nitrogen in the metal organic chemical vapor deposition epitaxy. The effects of the NH₃/N₂ 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/N₂ molar flow rate from ∼2 × 10⁻⁸ to ∼2 × 10⁻⁶ mol/min, the N impurities incorporated into the β-Ga₂O₃ increased linearly from ∼1 × 10¹⁸ to ∼2 × 10²⁰ cm⁻³. At low substrate temperatures (<800 °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 MΩ for a film grown with [N] ≈ [H] of ∼8 × 10¹⁸ cm⁻³. X-ray on-axis (020) and off-axis (111) rocking curve ω-scans and atomic force microscopy measurements show no influence of NH₃/N₂ dopant on the structural and surface quality of the films. However, the presence of H promoted the growth of (110) and ( 1 ¯ 10) facets elongated along the [001] direction. At high growth temperatures (≥950 °C), the H concentration in the films was reduced by nearly ∼10×, but with a slight increase in the concentration of N. The results show that controllable and repeatable nitrogen doping into β-Ga₂O₃ can be achieved using ammonia to obtain deep acceptor doping or compensation needed for device engineering in β-Ga₂O₃-based power electronic devices. [ABSTRACT FROM AUTHOR]