High performance 0.1 μm gate-length p-type SiGe MODFET's and MOS-MODFET's

Abstract

High performance p-type modulation-doped field-effect transistors (MODFET's) and metal-oxide-semiconductor MODFET (MOS-MODFET) with 0.1 /spl mu/m gate-length have been fabricated on a high hole mobility SiGe-Si heterojunction grown by ultrahigh vacuum chemical vapor deposition. The MODFET devices exhibited an extrinsic transconductance (g/sub m/) of 142 mS/mm, a unity current gain cut-off frequency (f/sub T/) of 45 GHz and a maximum oscillation frequency (f/sub MAX/) of 81 GHz, 5 nm-thick high quality jet-vapor-deposited (JVD) SiO/sub 2/ was utilized as gate dielectric for the MOS-MODFET's. The devices exhibited a lower gate leakage current (1 nA//spl mu/m at V/sub gs/=6 V) and a wider gate operating voltage swing in comparison to the MODFET's. However, due to the larger gate-to-channel distance and the existence of a parasitic surface channel, MOS-MODFET's demonstrated a smaller peak g/sub m/ of 90 mS/mm, f/sub T/ of 38 GHz, and f/sub max/ of 64 GHz. The threshold voltage shifted from 0.45 V for MODFET's to 1.33 V for MOS-MODFET's. A minimum noise figure (NF/sub min/) of 1.29 dB and an associated power gain (G/sub a/) of 12.8 dB were measured at 2 GHz for MODFET's, while the MOS-MODFET's exhibited a NF/sub min/ of 0.92 dB and a G/sub a/ of 12 dB at 2 GHz. These DC, RF, and high frequency noise characteristics make SiGe/Si MODFET's and MOS-MODFET's excellent candidates for wireless communications.