1261 The Morphology of CdTe Deposited by OMVPE: The Effect of Substrate Misorientation 1261 Special Issue Paper Journal of Electronic Materials, Vol. 26, No. 10, 1997 INTRODUCTION The quality of CdTe and Hg 1–x Cd x Te grown by orga- nometallic vapor phase epitaxy (OMVPE) 1–5 and mo- lecular beam epitaxy (MBE) 6,7 depends on the crystal- lographic orientation of the substrate. Epitaxial lay- ers grown on CdTe{100} show good crystalline quality but poor surface morphology because of the formation of pyramidal facets. 7 Epilayers grown on CdTe{111} are free of facets but the films are twinned. 3,6,8 Several investigators have reported the improvement of sur- face morphology on vicinal {100} substrates. Capper et al. 3 and Bhat and Ghandhi 4 found that the surface morphology of Hg 1–x Cd x Te was improved when CdTe{100} substrates were misoriented between 2–4° toward the (110) plane. D’yakonov et al. 1 studied CdTe growth on a spherical depression in a GaAs(100) substrate using OMVPE and found that the density of facets decreased almost to zero with a misorientation of 2.7° toward azimuth [110] and 3.5° toward azimuth [1 10]. Hamilton et al. 5 confirmed the results of D’yakonov et al. in their deposits of CdTe on a GaAs lens. Snyder et al. 2 also observed a remarkable change of film morphology for 3.8–4.8° misorientation toward <111> Te following homoepitaxial growth of CdTe on a lenticular substrate. Mitra et al. 9–11 in fact have taken advantage of the smooth morphology obtained on {100}4° → <111> Te and other misorientations of Cd 0.96 Zn 0.04 Te by using such substrates for deposition of Hg x Cd 1–x Te. These investigations demonstrate that the substrate crystallographic misorientation strongly affects the formation of facets and that the effect can be commercially significant. The mechanism for the formation of facets on CdTe{100} has been a subject of discussion in the literature. Facets might form by the nucleation of adsorbed Cd and Te atoms into three-dimensional islands, from which growth proceeds on {111} sur- faces. 8 Another possibility is that Te clusters on ter- races are the source of dislocations and stacking faults that can lead to the formation of facets. 2,12 Hamilton et al. 13 showed large facets forming from deposited particles, but their cross-sectional trans- mission electron microscopy (TEM) study of Cd 1–y Zn y Te epilayers also demonstrated that small, low angle facets on the same film were single crystals free of planar defects, and there was no clear relation- ship of dislocations and stacking faults to the facets. 13 Experimental and theoretical contributions to the general area of coarsening of singular surfaces pro- vide a foundation for understanding facet formation in systems as diverse as GaAs epitaxy and Fe epit- (Received March 14, 1997; accepted April 28, 1997) The Morphology of CdTe Deposited by Organometallic Vapor Phase Epitaxy: The Effect of Substrate Misorientation K. YONG, P.J. SIDES, and A.J. GELLMAN Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 Substrate misorientation and growth temperature influence the morphology of CdTe epilayers grown by organometallic vapor phase homoepitaxy. These effects were investigated by using CdTe{100} and CdTe{100} misoriented by 2, 4, 6, and 8° toward <111> Te as substrates for growth in the temperature range from 337 to 425°C. Low angle pyramidal facets appeared on films grown on the CdTe(100) surface. The number density of these pyramidal facets decreased to zero as the substrate misorientation angle increased to 4°. At higher misorientation angles, low angle protrusions, resembling fish scales, appeared on the surface. When the temperature was increased, facet size decreased but facet density increased. The film morphology at the high misorientations, however, improved remarkably with increasing temperature. Cross-sectional transmission electron microscopy provided evidence that both the faceted CdTe films and films with a mirror-like finish were epitaxial single crystals with no planar defects. Schwoebel barriers are suggested as the reason for the faceting of the surface grown on CdTe{100}. Key words: Cadmium telluride, facets, morphology, organometallic vapor phase epitaxy (OMVPE)