Simultaneous drive-in of Mg and disassociation of Mg-H complex in Ga2O3 by oxygen annealing achieving remarkable current blocking

Abstract

In order to increase the concentration of Mg in single crystal and epitaxial Ga2O3 solely via diffusion doping technique, different variations of diffusion methods are explored. First, a one-step infinite-source diffusion is compared with a two-step finite-source diffusion. The two-step diffusion is shown to be effective in increasing the Mg concentration in Ga2O3 by nearly 10 times. Furthermore, it was observed that the ambient gas used in the second step diffusion plays a critical role in Mg diffusion. The SIMS result is compared between a sample with second step diffusion in oxygen and another sample in a nitrogen ambient while keeping all other conditions identical. The presence of oxygen gas in the second step annealing is shown to be essential to the increase in Mg concentration and the disassociation of the Mg-H complex. Finally, the current–voltage blocking characteristics of the formed Mg-diffused current blocking layers are measured and are observed to have significantly increased from ∼500 V to more than 1 kV with the achieved Mg diffusion concentration profiles. The two-step oxygen-assisted Mg diffusion doping technique has shown to be a simple yet useful doping tool that paves the way for the realization of various high-power Ga2O3 electron devices.