Characteristics of ultrathin [4-7 nm] gate oxides for SiGe quantum well MOS structures

SiGe quantum well metal-oxide-semiconductor (MOS) structures were realized by the preparation of the undoped Si buffer layer, the undoped SiGe quantum well layer, and the undoped Si cap layer by molecular-beam epitaxy or low pressure chemical vapor deposition, and low thermal budget rapid thermal ox idation of the Si cap layer in dry oxygen at 1100 degrees C for 30-65 s. Co mprehensive electrical characterization by steady state admittance spectros copy was carried out. The relaxation of the strained SiGe layer was monitor ed by x-ray diffraction. The effects of the composition of the SiGe layer [ Ge content, and minute C content] on the trap density and the device charac teristics were investigated. Also examined were the effects of the oxidatio n temperature, the post-oxidation annealing [temperature and time] in nitro gen, and the post-metallization annealing [temperature and time] in forming gas, on the trap density and the device admittance characteristics.