Planar doping of p-type ZnSe layers with lithium grown by molecular beam epitaxy

Abstract

High quality p-type ZnSe layers with hole concentrations of 3 × 10 17 − 1.4 × 10 18 cm -3 have been grown using a planar doping technique employing lithium during molecular beam epitaxy (MBE). The Li-doping is investigated by reflection high energy electron diffraction (RHEED). It is found that islands of Li 2Se are formed on the growing ZnSe surface in the case of heavy Li doping. Secondary ion mass spectroscopy (SIMS) and photoluminescence (PL) are used to characterize the layers grown. SIMS analysis shows an abrupt change in Li concentration at the interface between highly doped (mid 10 19 cm -3) and undoped layers. This is the first report of the successful suppression of Li diffusion. PL spectra at 4.2 K show dominant acceptor-bound exciton emission (I 1). The line shape of I 1 is noticeably broadened with a tail towards the low energy side. This may be explained in terms of a Stark effect on bound excitons arising from charged impurities.