Optical properties of planar and selectively grown SiGe/Si multiple quantum wells

Abstract

An `ultra clean' atmospheric pressure chemical vapor phase deposition (APCVD) system has been used to grow SiGe/Si quantum well structures on planar and patterned substrates. The optical properties have been analyzed by photoluminescence (PL) and the effect of growth temperature, well width, and Ge concentration on the PL properties has been studied. Phonon resolved spectra were obtained for growth temperatures exceeding 600 degree(s)C for selective and non-selective growth. Spectra taken from selectively grown samples reveal additional lines related to dislocations and twin formation. Twinning was found predominantly along the (110) direction of the SiO<SUB>2</SUB>/Si interface, whereas interfaces along the (100) direction had a much lower defect density. Temperature resolved measurements indicate a free exciton like behavior for the no-phonon (NP) line of the SiGe quantum wells. Time resolved measurements show decay times of the SiGe NP-line in the range of 0.5 to 0.8 microsecond(s) , comparable to those found for the Si TO phonon line. This demonstrates the capability of APCVD to grow selectively and non-selectively SiGe/Si quantum well structures with low defect densities.