Observation of deep-level-free band edge luminescence and quantum confinement in strained Si1−xGex/Si single quantum well structures grown by solid source Si molecular beam epitaxy

Abstract

Well‐resolved band edge luminescence with no deep level emissions is reported for Si_0.8Ge_0.2/Si single quantum well (SQW) structures grown at high substrate temperatures (T_s≊620 °C) by solid source Si molecular beam epitaxy (MBE). No‐phonon (NP) transitions due to symmetry‐breaking alloy disordering in SiGe layers and transverse optical (TO) phonon replicas were clearly identified. With decreasing well width, NP and TO emissions were found to show systematic blue shift due to quantum confinement effect. Excellent crystal quality was evidenced by total absence of defect‐related deep level emissions characteristic of photoluminescence spectra of samples grown at lower temperatures, T_s<600 °C. This result indicates that high growth temperature environment is essential to efficient radiative recombination in SiGe/Si QW structures.