Poly-Si gate electrodes for AlGaN/GaN HEMT with high reliability and low gate leakage current

• Gate leakage current of AlGaN/GaN HEMT can be drastically decreased by adopting poly-Si gate electrode.
• By combining BF2 implantation the threshold voltage can be shifted toward positive direction.
• Owing to reduced gate leakage current, the device has high reliability against strong reverse bias stressing.

AlGaN/GaN HEMT with a BF2-implanted polycrystalline Si gate has been characterized through comparison to TiN gate electrodes. Positive threshold voltage (Vth) shift was observed with the addition of F ions, which in turn degraded the effective electron mobility (μeff) by diffusion into the AlGaN/GaN interface and GaN layer. A large reduction in gate leakage current (Jg) was achieved and the property was maintained even after strong reverse-bias stressing. No additional degradation in μeff was observed, suggesting the formation of a stable poly-Si/AlGaN interface. Therefore, poly-Si gate electrodes have advantages in reducing the Jg and robustness against reverse-bias stressing.