Strained silicon and silicon-germanium quantum devices by chemical vapor deposition

Strained SiGe band-to-band tunneling (BTBT) devices and strained Si two-dimensional electron gases (2DEGs) are promising for low-power and quantum computing applications. The objective of this dissertation is to pursue the fundamental understanding of BTBT in strained SiGe films and electron transport properties in strained Si.;We report the first quantitative study of BTBT in strained p+ -SiGe/n+-Si heterojunctions and p+-SiGe/n +-SiGe homojunctions at forward and reverse biases. Negative differential resistance (NDR) at forward bias is clearly observed for each device, with the highest observed peak current density of 104 A/cm 2. In reverse bias, a BTBT current density of 106 A/cm 2 is measured and a model comparison with good agreement is also presented. Furthermore, we demonstrate that the precise modeling of reverse-biased BTBT devices requires the observation of NDR in forward bias.;The surface segregation of phosphorus in relaxed SiGe films is studied with an extremely sharp phosphorus turn-off slope of 6 nm/decade reported. This enables effective Schottky gating on a depletion-mode device of a Si two-dimensional electron gas (2DEG). We also investigate the effect of surface hydrogen on phosphorus segregation. A phenomenological model for this segregation is proposed to explain the experimental results with good agreement.;A 2DEG with a record high mobility of 522,000 cm2/V-s in an isotopically enriched 28Si quantum well is presented. The estimated electron dephasing time of ~ 2 mus is presented. We investigate the effects of different layers in a Si 2DEG structure on electron mobility and conclude that the remote impurity charges are the dominant source for electron scattering. The reduced segregation of phosphorus enables an inverted modulation-doped Si 2DEG with extremely high mobility of 470,000 cm 2/V-s. For the first time second subband occupancy was achieved in a Si quantum well.