Optimization of NiO/β-Ga2O3 Heterojunction Diodes for High-Power Application

This work presents the optimization of a NiO/ $\beta $ -Ga2O3 heterojunction diode (HJD) by adjusting the structural parameters of the NiO layer. A rapid thermal annealing (RTA) process was utilized to modulate the hole concentration of the sputtered NiO. The influence of the NiO layer geometry and its hole concentration on the HJDs' electrical properties has been thoroughly investigated and discussed based on both the experimental study and the technology computer-aided design (TCAD) simulation. It was found that the forward current of the HJDs was mainly determined by the size of the anode electrode regardless of the NiO layer dimension, indicating the poor current spreading within the NiO film. Enlarging the NiO layer dimension with a fixed anode or adjusting the hole concentration to an optimal value could benefit the device breakdown voltage ( ${V}_{B}$ ) by reducing the electric field crowding effect. An optimum value of ${\sim }2\,\, {}\times {} 10^{17}$ cm−3 was determined for the HJDs with a drift layer doping concentration of $1.8\,\, {}\times {}10^{16}$ cm−3. To achieve a good balance between ${V}_{B}$ and the specific ON-resistance ( ${R}_{{\mathrm {ON,sp}}}$ ), a double-layer structure ( $\text{p}^{+}$ NiO/ $\text{p}^{-}$ NiO) was adopted and optimized, yielding a greatly enhanced performance in the NiO/ $\beta $ -Ga2O3 HJDs. The results provided a useful insight into the $\text{p}^{-}$ NiO-related $\beta $ -Ga2O3 power device design.