Gallium nitride (GaN)-based high electron mobility transistor (HEMT) power devices have demonstrated great application potential due to high current density, high switching speed, and low ON-resistance in comparison to the established silicon (Si)-based semiconductor devices. These superior characteristics make GaN HEMTs emerge as promising candidates for next-generation power converters.

Recently, Prof. ZHANG Baoshun's group, at Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences,reveals high performance AlGaN/GaN MIS-HEMTs. The gate dielectric layer and surface passivation layer are formed by the low pressure chemical vapor deposition (LPCVD) Si₃N₄. The LPCVD-Si₃N₄ MIS-HEMTs exhibit a high breakdown voltage 1162 V at I_DS = 1 µA/mm, a low OFF-state leakage of 7.7 × 10^-12 A/mm and an excellent ON/OFF current ratio ~ 10¹¹. Compared with the static ON-resistance of 2.88 mΩ·cm², the dynamic ON-resistance after high OFF-state drain bias stress at 600 V only increases to 4.89 mΩ·cm². The power device figure of merit (FOM = BV²/R_ON.sp) is calculated as 469 MW·cm^-2. The LPCVD-Si₃N₄/GaN interface state density is in the range of (1.4-5.3) × 10¹³ eV^-1 cm^-2 extracted by conventional conductance method. Finally, the gate insulator degradation of GaN-based MIS-HEMTs is analyzed by time-dependent-dielectric breakdown (TDDB) test. The lifetime is extrapolated to 0.01% of failure after 10 years at 300 K by fitting the data with a power law to gate voltage of 10.1 V. These results prove a great potential of LPVCD-Si₃N₄/AlGaN/GaN/Si MIS-HEMTs for high power switching applications.This work has been published in the journal Electron Devices, IEEE Transactions on, 2015, 63(2): 731 - 738.

This work was partly supported by the Key Technologies Support Program of  Jiangsu  Province  (grant  No. BE2013002-2). And the authors are grateful for the technical support provided by Nanofabrication Facility and Platform for Characterization and Test of SINANO, Chinese Academy of Science.

Fig. 1.  Schematic of an AlGaN/GaN MIS-HEMT with 20 nm Si₃N₄ as a gate dielectric and passivation layer.(Image by ZHANG Baoshun's group)