Improved Noise and Device Performances of AlGaN/GaN HEMTs with In Situ Silicon Carbon Nitride (SiCN) Cap Layer

Abstract

We investigated the effects of in situ silicon carbon nitride (SiCN) cap layer of AlGaN/GaN high-electron mobility transistors (HEMTs) on DC, capacitance-voltage (C-V) and low-frequency noise (LFN). The proposed device with SiCN cap layer exhibited enhanced drain current, reduced gate leakage current, low interface trap density (Dit), and high on/off ratio thanks to the passivation effect, compared to the device without SiCN cap layer. Both devices clearly showed 1/f noise behavior with carrier number fluctuations (CNF), regardless of the existence of SiCN cap layer. The proposed device presented the relative low trap density (Nit) and reduced access noise due to the effective surface passivation in source-drain access region compared to the device without SiCN cap layer. From the improved DC, C-V and noise results of the proposed device, the in situ SiCN cap layer plays an important role in the passivation layer and gate oxide layer in AlGaN/GaN HEMT.

Keywords

• AlGaN/GaN
• HEMTs
• cap layer
• low-frequency noise
• carrier number fluctuations