Abstract
A high threshold voltage (VTH) normally off GaN MISHEMTs with a uniform threshold voltage distribution (VTH = 4.25 ± 0.1 V at IDS = 1 μA/mm) were demonstrated by the selective area ohmic regrowth technique together with an Si-rich LPCVD-SiNx gate insulator. In the conventional GaN MOSFET structure, the carriers were induced by the inversion channel at a high positive gate voltage. However, this design sacrifices the channel mobility and reliability because a huge number of carriers are beneath the gate insulator directly during operation. In this study, a 3-nm ultra-thin Al0.25Ga0.75N barrier was adopted to provide a two-dimensional electron gas (2DEG) channel underneath the gate terminal and selective area MOCVD-regrowth layer to improve the ohmic contact resistivity. An Si-rich LPCVD-SiNx gate insulator was employed to absorb trace oxygen contamination on the GaN surface and to improve the insulator/GaN interface quality. Based on the breakdown voltage, current density, and dynamic RON measured results, the proposed LPCVD-MISHEMT provides a potential candidate solution for switching power electronics.
Highlights
In recent years, GaN-based normally off high-electron-mobility transistors (HEMTs) have been implemented for switching power electronics due to their wide energy bandgap, high electron mobility, and high current density [1,2,3]
We proposed an Si-rich SiN gate insulator grown by LPCVD to absorb the oxygen atom on the native AlGaN barrier layer surface and narrow the oxygen contamination region between
Drain/source regions were adopted to demonstrate a low on-resistance (RON ) ultra-thin barrier (UTB) GaN MISHEMT with a large positive VTH performance
Summary
GaN-based normally off high-electron-mobility transistors (HEMTs) have been implemented for switching power electronics due to their wide energy bandgap, high electron mobility, and high current density [1,2,3]. To overcome the etching damages and VTH uniformity issues of the gate-recess-type normally off GaN HEMT, ultra-thin-barrier (UTB) AlGaN/GaN heterostructures with an MIS gate architecture were proposed [10,11,12]. All of these previous studies adopted PEALD (plasma-enhanced atomic layer deposition) as the gate insulator to minimize the plasma-induced damage during gate insulator. To further improve the ohmic contact resistivity, the MOCVE-regrown AlGaN drain/source regions were adopted to demonstrate a low on-resistance (RON ) ultra-thin barrier (UTB) GaN MISHEMT with a large positive VTH performance
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