Growth of p-type ZnTe and n-type CdSe films on GaAs 001/by pulsed laser ablation

Thin films of p-type ZnTe and n-type CdSe were deposited on 001.and 28-miscut GaAs wafers by ArF 193 nm.pulsed laser ablation of stoichiometric ZnTe and CdSe targets through several ambient gas compositions and total pressures. Films were grown both with the substrate facing the plume fs08.and with the substrate rotated by an angle, f)08. Substrates were affixed to the heater using conventional indium bonding and an indium-free method. Hall effect measurements were performed to determine the influence of target-to-substrate separation DTS., substrate temperature, gas composition and total pressure, substrate orientation f., bonding method, and substrate miscut on the carrier concentration and mobility. NH3 was found to be largely ineffective for p-type doping of ZnTe under the conditions explored and especially when compared to the wide range of resistivities achievable by employing nitrogen. In one instance, however, a free-hole concentration of 2=1018 cmy3 mf3 cm2rVPs.was achieved by depositing at a large distance DTSs17.5 cm. and low temperature 2008C.in 20 mTorr of NH3. The Hall effect data for CdSe were found to cluster into two distinct regimes, one with mobilities F0.3 cm2rVPs and carrier concentrations G3=1020 cmy3, the other with mobilities G30 cm2rVPs and carrier concentrations F4=1018 cmy3. Examination of X-ray diffraction data coupled with reflection high-energy electron diffraction RHEED.measurements, observations of the films’ surfaces, and secondary ion mass spectroscopy SIMS.profiling, indicated that no single-growth parameter was responsible for the observed bimodal behavior. q1998 Elsevier Science B.V.