Over 1200 V Normally-OFF p-NiO Gated AlGaN/GaN HEMTs on Si With a Small Threshold Voltage Shift
Hui Guo, Hehe Gong, Pengfei Shao, Xinxin Yu, Jin Wang, Rui Wang, Le Yu, Jiandong Ye, Dunjun Chen, Hai Lu, Rong Zhang, Youdou Zheng
Abstract
In this letter, we demonstrated a normally-off AlGaN/GaN HEMT using p-NiO as a gate stack combined with a recess structure. The fabricated HEMT exhibits a positive threshold voltage of 1.73 V, a saturation output current of 524 mA/mm, a small subthreshold swing of 79.7 mV/dec and a maximum transconductance as high as 143 mS/mm. This is the first time to demonstrate the breakdown characteristics of a p-NiO gate HEMT with a high breakdown voltage of 1205 V and a low specific ON-resistance of 2.22 <inline-formula> <tex-math notation="LaTeX">$\text{m}\Omega \cdot $ </tex-math></inline-formula>cm<sup>2</sup>, yielding a competitive Baliga’s figure-of-merit of 0.65 GW/cm<sup>2</sup>. The instability evaluation of <inline-formula> <tex-math notation="LaTeX">${V}_{\text {TH}}$ </tex-math></inline-formula> by step stress and pulse transfer curves shows that the p-NiO gate HEMT has a negligible <inline-formula> <tex-math notation="LaTeX">${V}_{\text {TH}}$ </tex-math></inline-formula> shift in the entire measured gate bias range, which can be attributed to the counteraction between the electron trapping-induced positive <inline-formula> <tex-math notation="LaTeX">$\text{V}_{\text {TH}}$ </tex-math></inline-formula> shift and hole accumulation induced-negative <inline-formula> <tex-math notation="LaTeX">${V}_{\text {TH}}$ </tex-math></inline-formula> shift. It is well understood in terms of the carrier transport model based on the large band discontinuity at the interface of the p-NiO/AlGaN type-II heterojunction, which is further verified by transient gate current spectra.