SI SIGE FIELD-EFFECT TRANSISTORS

Over the last few years, SiGe heterodevices with outstanding rf perfor mance have been introduced to meet the needs of modern consumer electr onics, which require novel silicon-based low cost-high speed component s with improved current gain, low noise, and reduced power consumption operating in the GHz range. This article reviews device and the first circuit results of lateral modulation doped SiGe modulation doped het ero-field-effect transistors (MODFETs) with Schottky gates as well as lateral and vertical SiGe metalorganic field effect transistors (MOSFE Ts) focusing on de characteristics, rf performance comprising cutoff f requencies, delays, and on layer design. With an f(max), of up to 92 G Hz, the highest maximum frequency of oscillation reported so far for a ny Si-based FET, and transconductances g(me) up to 470 mS/mm, the n-Si Ge MODFET is presently improving in speed with combining the advantage s of heterodevices with well-established Si technology. For p-SiGe MOD FETs cutoff frequencies f(t) of 70 GHz and f(max) of 84 GHz have been measured. A reduced gate leakage and an improved voltage swing is achi eved using MOS-gated heterodevices. For p-channel SiGe hetero-MOSFETs room temperature transconductances up to 210 mS/mm for 0.25 mu m gate- length devices have been measured. Vertical MOSFETs allow further devi ce scaling into the deep sub-100 nm range and thus enable us to overco me performance limits due to minimum feature sizes using state-of-the- art lithography techniques. (C) 1998 American Vacuum Society.