NITROGEN DOPING OF MOLECULAR-BEAM EPITAXIALLY GROWN CDTE WITH A RADIOFREQUENCY PLASMA SOURCE

We report on the use of an Oxford Applied Research MPD21 Atom/Radical RF source to dope CdTe layers with nitrogen (N). The layers were grown in a VG V80H MBE system, using CdTe as the source material. Photoluminescence (PL) measurements give evidence of N incorporation in our CdTe: N layers, as signified by an increase in intensity of the N acceptor bound exciton (ABE) line and the associated donor-acceptor pair (DAP) band, with increasing plasma RF power. The presence of N was confirmed using secondary ion mass spectrometry (SIMS). In addition, PL and SIMS results show the presence of significant levels of antimony (Sb) in the N-doped layers. The Sb acceptor depth was found to be 52 meV from observation of the associated free to bound transition. The unintentional presence of Sb is tentatively attributed to enhanced autodoping from the substrate, caused by the presence of N. Like the undoped layers, the N-doped samples are found to be n-type, but the carrier concentrations are < 10(15) cm-3.