Effects of GaN Buffer Resistance on the Device Performances of AlGaN/GaN HEMTs

Ki-Sik Im,Sung Jin An,Yeo Jin Choi,Jae-Hoon Lee

doi:10.3390/cryst10090848

Ki-Sik Im, Sung Jin An + Show 2 more

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https://doi.org/10.3390/cryst10090848

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Abstract

We investigated the effects of GaN buffer resistance of AlGaN/GaN high-electron-mobility transistors (HEMTs) on direct current (DC), low-frequency noise (LFN), and pulsed I-V characterization performances. The devices with the highest GaN buffer resistance were grown on sapphire substrate using two-step growth temperature method without additional compensation doping. The proposed device exhibited the degraded off-state leakage current due to the improved GaN buffer quality compared to the reference devices with relative low buffer resistance, which is confirmed by high resolution X-ray diffraction (HRXRD). However, the proposed device with deep-level defects in GaN buffer layer showed the reduced hysteresis (∆Vth), increased breakdown voltage (BV), and enhanced pulse I-V characteristics. Regardless of GaN buffer resistance, all devices clearly showed 1/f behavior with carrier number fluctuations (CNF) at on-state but followed 1/f2 characteristic at off-state. From the 1/f2 noise characteristics, the extracted trap time constant (τi) of the proposed device can be obtained to be 10 ms, which is shorter than those of the reference devices because of the full compensation of deep-level defects in the GaN buffer layer.

Highlights

AlGaN/GaN high-electron-mobility transistors (HEMTs) have many advantages for power device applications because of their excellent material properties such as high band-gap and large breakdown electric field
Materials and Methods plain sapphire substrate by metal organic chemical vapor deposition, which consists of 30-nm-thick low-temperature-grown initial GaN layer, 3-μm-thick highly resistive undoped GaN buffer layer, The AlGaN/GaN heterostructures with different GaN buffer resistance were grown on a 4-in and 25-nm-thick AlGaN barrier
The proposed device using two-step growth exhibits the positive shift positive shift of threshold voltage (Vth) with approximately –3 V compared to the reference devices

Summary

Introduction

AlGaN/GaN high-electron-mobility transistors (HEMTs) have many advantages for power device applications because of their excellent material properties such as high band-gap and large breakdown electric field. Many technologies for developing the HR GaN buffer layer have been reported by utilizing (1) the generation of the deep-level defects or dislocations through controlling the growth temperature [1,2] and (2) the doping of deep-level impurities such as Fe, Mg, or C atoms [3,4,5]. These deep-level defects and impurities mostly compensate the background n-type residual donors in conventional unintentional doped GaN buffer layer due to the nitrogen vacancies (V N ) and/or oxygen (O) atoms. Lee et al [1] reported to the device performances of normally off

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Conclusion