Effective Hole Mobility in SiGe Buried-Channel Quantum Well MOSFETs on SOI by Low-Pressure CVD

The effective hole mobility of buried-channel SiGe quantum well metal-oxide-semiconductor field-effect-transistors (MOSFETs) on silicon-on-insulator (SOI) was verified. The buried-channel structures consisted of a single quantum well and triple quantum wells which were deposited on a SIMOX (separation by implantation of oxygen) substrate at 550 degrees C by low-pressure chemical vapor deposition (CVD). The growth apparatus was built based on ultra-clean technology. The Ge fraction of the alloy was 0.2 and 0.4 and a MOSFET with a 5.9 nm-thick gate oxide was fabricated on the well layers. The effective hole mobility versus effective electric field for the devices was obtained at room temperature. The mobility of triple Si0.8Ge0.2 quantum well device was enhanced by nearly 2 times compared to the single quantum well device. This enhancement which depended upon the ground energy level of the triple quantum wells was caused by the increase of holes trapped in the buried channel. The enhancement of single Si0.6Ge0.4 quantum well device was 60%, although the hole mobility was promoted as the Ge fraction in the alloy increased. The reason was due to the crystalline quality degradation. (C) 2013 The Electrochemical Society. All rights reserved.