Abstract
In this work, novel hybrid gate Ultra-Thin-Barrier HEMTs (HG-UTB HEMTs) featuring a wide modulation range of threshold voltages (VTH) are proposed. The hybrid gate structure consists of a p-GaN gate part and a MIS-gate part. Due to the depletion effect assisted by the p-GaN gate part, the VTH of HG-UTB HEMTs can be significantly increased. By tailoring the hole concentration of the p-GaN gate, the VTH can be flexibly modulated from 1.63 V to 3.84 V. Moreover, the MIS-gate part enables the effective reduction in the electric field (E-field) peak at the drain-side edge of the p-GaN gate, which reduces the potential gate degradation originating from the high E-field in the p-GaN gate. Meanwhile, the HG-UTB HEMTs exhibit a maximum drain current as high as 701 mA/mm and correspond to an on-resistance of 10.1 Ω mm and a breakdown voltage of 610 V. The proposed HG-UTB HEMTs are a potential means to achieve normally off GaN HEMTs with a promising device performance and featuring a flexible VTH modulation range, which is of great interest for versatile power applications.
Highlights
High-electron-mobility transistors (HEMTs) based on AlGaN/GaN heterostructures are promising for use in high-frequency and high-power applications due to their high breakdown voltage (BV) and polarization-induced two-dimensional electron gas (2DEG) at the interface of the AlGaN/GaN heterojunction [1]
The p-GaN gate facilitates the enhancement of the depletion of the 2DEG channel, which further raises the energy band of the ultra-thin barrier heterojunction and results in a more positive VTH in the proposed HGUTB HEMTs
The electric field (E-field) crowing located at the p-GaN edge is effectively mitof the depletion of the 2DEG channel, which further raises the energy band of the ultra-thin barrier heterojunction and results in a more positive V TH in the proposed HG-UTB HEMTs
Summary
High-electron-mobility transistors (HEMTs) based on AlGaN/GaN heterostructures are promising for use in high-frequency and high-power applications due to their high breakdown voltage (BV) and polarization-induced two-dimensional electron gas (2DEG) at the interface of the AlGaN/GaN heterojunction [1]. The p-GaN gate HEMTs are commercialized to obtain E-mode operation, in which the p-GaN cap layer is inserted between the gate metal and AlGaN barrier to deplete the 2DEG beneath the gate [13]. The positive charges will enhance the 2DEG density in the access region, which can reduce the on-resistance of the device In this manner, the intrinsic E-mode channel is reserved beneath the gate region, while the access region features a low on-resistance [20,21,22]. The proposed device structure and the concept of hybrid gate design are of great interest for fabricating the E-mode GaN power HEMTs with a flexible VTH modulation range to accommodate different applications
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