Silicon carbide: from amorphous to crystalline material

Silicon carbide is a wide band gap semiconductor with a large variety of atomic configuration both in the crystalline as well as in the amorphous phase. The structure and properties of silicon carbide depend on the preparation conditions. Amorphous SiC (a-SiC) can be easily prepared by low temperature (400 °C) chemical vapour deposition (CVD) from the SiH4/CH4 gas mixture, and hydrogen incorporation allows to decrease the defect density down to 1017 cm−3 and to obtain high luminescent yield material. At 900 °C solid phase epitaxy takes place on (1 1 2 0) and (0 0 0 1) substrates, and the residual disorder depends on the crystallographic orientation. At 1650 °C CVD at low pressure on single crystal gives free-of-defects layer (1014 cm−3) with high electron mobility up to 400 cm2 V−1 s−1 for 4H substrate. High growth rate (1 mm/h) for SiC bulk is reached with sublimation process at temperature as high as 2400 °C, however, macroscopic defects as micropipes or polytype inclusions are present. Intrinsic defects, vacancy or interstitial-type, introduced during the growth or intentionally by kiloelectronvolt ion implantation, can be removed after a thermal treatment at 1500 °C. Good performance optical and electrical devices are already fabricated with amorphous and crystalline silicon carbide.