Si/SiGe/Si heterostructure growth without interface roughness at high germanium mole fractions by low temperature low pressure chemical vapour deposition

A new low temperature low pressure chemical deposition process for Si/SiGe/Si heterostructures containing high germanium mole fractions has been developed. The silicon surface and the SiSiGe interface roughness strongly depend on the deposition temperature and the germanium concentration. For germanium concentrations around 20%, flat surfaces can be realized at 550 °C. High concentrations of more than 50% Ge require much lower growth temperatures, namely 450 °C for SiGe and 525 °C for the silicon capping layer. A new optimized process sequence is given to grow Si/SiGe/Si heterostructures with atomically flat surfaces and interfaces containing more than 50% Ge.