Sub-30-nm In0.8Ga0.2As Composite-Channel High-Electron-Mobility Transistors With Record High-Frequency Characteristics

Abstract

We present sub-30-nm In0.8Ga0.2As composite-channel high-electron-mobility transistors (HEMTs) with outstanding dc and high-frequency characteristics. We adopted a composite-channel design with an In0.8Ga0.2As core layer, which led to superior carrier transport properties such as a Hall mobility (μn_Hall) of 13 500 cm2/V·s. The device with Lg = 19 nm exhibited an excellent combination of dc and RF properties, including RON = 271-μm, gm_max = 2.8 mS/μm, and fT/fmax = 738/492 GHz. To understand the physical origin of such an excellent combination of dc and RF responses,we analyzed the effective mobility (μn_eff) and delay time for both longand short-Lg devices, revealing a very high μn_eff value of 13 200 cm2/V·s and an average velocity under the gate (vavg) of 6.2 × 107 cm/s. We also studied the impact of the electrostatic integrity of the device, finding that the intrinsic output conductance (goi) played a role in determining fT and fmax in short-Lg HEMTs.