Optimization of NiO/<i>β</i>-Ga<sub>2</sub>O<sub>3</sub> Heterojunction Diodes for High-Power Application
Chao Liao, Xing Lü, Tongling Xu, Paiwen Fang, Yuxin Deng, Haoxun Luo, Zhisheng Wu, Zimin Chen, Jun Liang, Yanli Pei, Gang Wang
Abstract
This work presents the optimization of a NiO/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -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 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{B}$ </tex-math></inline-formula> ) by reducing the electric field crowding effect. An optimum value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\sim }2\,\, {}\times {} 10^{17}$ </tex-math></inline-formula> cm−3 was determined for the HJDs with a drift layer doping concentration of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.8\,\, {}\times {}10^{16}$ </tex-math></inline-formula> cm−3. To achieve a good balance between <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{B}$ </tex-math></inline-formula> and the specific ON-resistance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{{\mathrm {ON,sp}}}$ </tex-math></inline-formula> ), a double-layer structure ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{p}^{+}$ </tex-math></inline-formula> NiO/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{p}^{-}$ </tex-math></inline-formula> NiO) was adopted and optimized, yielding a greatly enhanced performance in the NiO/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ga2O3 HJDs. The results provided a useful insight into the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{p}^{-}$ </tex-math></inline-formula> NiO-related <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ga2O3 power device design.