Epitaxial Growth and Properties of Silicon on Alumina-Rich Single-Crystal Spinel

Abstract

Mobilities similar in magnitude to bulk silicon mobilities may be realized in 1.4 to 1.6µ thick films on flame fusion magnesium aluminate spinel, for carrier concentrations greater than (p‐type). The electrical properties of these films are not significantly altered by thermal oxidation at 1200° C for 1 hr. In this carrier concentration range the electrical characteristics are not highly dependent on the deposition rate within the limits investigated. For carrier concentrations between and (p‐type) the “as deposited” film mobilities are near bulk values, but the mobilities are degraded by the thermal oxidation. In this doping range the electrical properties of the oxidized films are critically dependent on the deposition rate. The films deposited at the higher rates are altered less on oxidation than films deposited at the lower rates. Using a growth rate of 2 µ/min, a mobility of 300 cm²/V‐sec (≈80% of bulk) at may be realized in a film oxidized 1 hr at 1100°C. Below this carrier concentration the mobility of the oxidized films decreases sharply with decreasing carrier concentrations. Minority carrier lifetimes as high as 40 nsec have been realized in 4µ thick films of silicon on spinel. The carrier concentration as a function of temperature and mobility as a function of thickness of silicon on spinel have been measured.