Growth of nitrogen-doped (010) β-Ga2O3 by plasma-assisted molecular beam epitaxy using an O2/N2 gas mixture

In this study, we report on the intentional nitrogen doping of plasma-assisted MBE (PAMBE)-grown (010) β-Ga2O3 films by generating the growth plasma with an O2 and N2 gas mixture. A nitrogen doping range of 1.3 × 1018 to 4.5 × 1019 cm−3 was achieved. The nitrogen doping profiles have top-hat shapes with sharp turn-on and turn-off. Nitrogen doping was found to have a negligible impact on surface morphology. Nitrogen incorporation was unaffected by gallium flux and growth temperatures over a large growth window. An incorporation dependence on plasma power and total gas flow rate was observed. This was attributed to the N2 triple bond strength compared to the O2 double bond strength, which makes N2 harder to crack in the plasma source. Increasing the plasma power from 140 to 230 W increased nitrogen incorporation by 1.6×, while increasing the total gas flow rate from 0.8 to 2.0 sccm decreased incorporation by 3.2×. The compensation effect of nitrogen was verified by characterizing effective carrier concentration in conducting tin and nitrogen co-doped films. A 2.1 V built-in voltage was extracted from a nitrogen-doped, n− junction device using CV measurements. The device was found to exhibit rectifying behavior with a 100 A/cm2 current density at 2.9 V. The junction demonstrated here can play a key role in field management and electrostatic engineering for β-Ga2O3-based power devices. Overall, the controllability of PAMBE nitrogen doping and the properties of nitrogen-doped films suggest PAMBE-grown, nitrogen-doped layers have promising power device applications.