Photoluminescence studies of Si (100) doped with low-energy (100–1000 eV) B+ ions during molecular beam epitaxy

Abstract

Temperature‐dependent photoluminescence (PL) measurements have been used to characterize 5‐μm‐thick Si(100) epitaxial layers doped in situ during molecular beam epitaxial growth with low‐energy (100, 500, and 1000 eV) ¹¹ B⁺ ions at growth temperatures of 500, 650, and 800 °C. Moderate doping (N_B ∼10¹⁷ cm⁻³) yielded PL features comprised of both sharp and broad peaks in the boron bound exciton (B‐BE) region. At 4.2 K a broad B‐BE feature near 1086 meV dominated, although the sharp transverse optical phonon‐assisted B‐BE peak (B¹_TO ) at 1092.5 meV was resolvable for N_B17 cm⁻³. Increasing the PL sample temperature above 4.2 K caused a rapid decay of the broad B‐BE peak intensity, thus permitting comparison of B¹_TO intensity for a range of ion energies and growth temperatures. At 10 K, a bulk‐like spectrum containing a sharp B¹_TO peak with weaker multiexciton peaks B²_TO and B³_TO was observed for the film growth at the highest temperature and lowest ion energy (800 °C and 100 eV). However, the intensity of the B¹_TO peak decreased with decreasing growth temperature (constant ion energy) and with increasing ion energy (constant growth temperature). Samples grown at the lowest temperature (500 °C) displayed very different PL spectra with much weaker line emission, a rising PL background, and additional lines near 1040 meV due to ion‐induced residual lattice defects. Quenching of B¹_TO and the other sharp B‐BE peaks was accompanied by an increase in the N1 peak at 745.7 meV.