Effect of growth temperature on photoluminescence from ion-beam-doped molecular beam epitaxial Si:As

Abstract

Abstract Low energy (500 eV) ion beam doping with As + ions during silicon molecular beam epitaxial growth has been exploited to obtain thick (about 5 microm) homo-epitaxial 3×10 16 cm −3 Si:As layers on n + (5×10 18 Sb doped) silicon substrates. These samples grown over a range of growth temperatures, 500–800 °C, were studied using low temperature (4.2 K) photoluminescence (PL) spectroscopy and deep-level transient spectroscopy (DLTS). The PL results for two growths, at 500 and 800°C, are presented here. Present in both spectra, although less intense for the 500°C sample, are three sharp lines due to the decay of arsenic-bound excitons: the no-phonon, transverse acoustic-phonon-assisted and transverse optic-phonon-assisted (TO) lines. A much broader and weaker Sb-BE(TO) peak from the nearly degenerate substrate was also observed. Only the higher temperature sample was free of the additional peaks (generally with lower energy than the arsenic-bound exciton peaks, due to residual ion-induced lattice defects) and the emission background rising below 900 meV for 500°C growth. This broad background signal appeared to be related to the presence of electron traps in the 500°C samples at a concentration of about 2×10 14 cm −3 as determined by DLTS. However, the 800°C sample was of much better electronic quality since it exhibited no electron traps in DLTS (sensitivity, approximately 10 13 traps cm −3 ) and had a PL spectrum containing only sharp, relatively intense, bulk-like bound exciton peaks.