CHARACTERIZATION OF INP AND GAINASP LAYERS PREPARED BY LIQUID-PHASE EPITAXY USING HOLMIUM DOPING AND GETTERING

A series of InP and GaInAsP (lambda(g) = 1.3 mu m) layer samples were prepared by liquid-phase epitaxy from melts containing 0-0.5 wt.% of t he rare-earth element holmium. The growth process was carried out in a horizontal multiple-bin graphite boat in a high-purity H-2 atmosphere . The layers were grown on (100)-oriented InP substrates at 630 degree s C. The samples were examined by various physical diagnostic techniqu es; among them, photoluminescence spectroscopy was the most important. There are no indications of the holmium ions being incorporated into the host lattice sites to form optically active centres. The impact of a Ho admixture is nonetheless quite dramatic, especially on the carri er density, which is decreased by two-and-a-half orders of magnitude, and on the photoluminescence spectra which become markedly narrowed an d their fine features are resolved. These effects are attributed to ho lmium acting as a very efficient gettering agent with regard to shallo w donors. A(III)B(V) semiconductor layers with low background carrier concentrations are of interest for high quality detectors and devices destined for very high frequency operation. (C) 1997 Elsevier Science S.A.