Traps inhomogeneity induced conversion of Shockley–Read–Hall recombination in NiO/β-Ga2O3 p+–n heterojunction diodes

In this Letter, the trap inhomogeneity within β-Ga2O3 is correlated with the conversion of Shockley–Read–Hall (SRH) recombination in NiO/β-Ga2O3 p+–n heterojunction diodes. For the virgin epi-wafer, both near-surface traps E2 (EC-0.82 eV) and E3 (EC-1.11 eV) and bulk E2* traps (EC-0.76 eV) are identified by a transient capacitance analysis, and the corresponding forward current–voltage characteristics of diodes are well fitted in the framework of field-dependent SRH recombination. The SRH recombination rates for E2, E3, and E2* traps are determined to be 1.3 × 107, 8.6 × 108, and 2.4 × 108 s−1, respectively. In this circumstance, carrier transport under forward bias is governed by trap-assisted tunneling through E3 traps with high recombination rates, and the hysteresis is pronounced. With the removal of the defective surface layer, E2 and E3 traps are almost completely eliminated, together with the reduced density of E2* traps to 5.6 × 1014 cm−3. The resultant diode performs an improved rectification ratio of >1011 at ±3 V and an enhanced reverse breakdown voltage of 1692 V. The elimination of near-surface traps leads to the conversion of carrier transport into the conventional SRH recombination, accompanied by the negligible forward hysteresis characteristics. The established fundamental correlation of carrier transport and traps within Ga2O3 is beneficial to develop a high-performance power rectifier toward practical applications.