Correlation of CdZnTe(211)B Substrate Surface Morphology and HgCdTe(211)B Epilayer Defects J. ZHAO, 1,4 Y. CHANG, 1 G. BADANO, 1 S. SIVANANTHAN, 1 J. MARKUNAS, 2 S. LEWIS, 2 J.H. DINAN, 2 P.S. WIJEWARNASURIYA, 3 Y. CHEN, 3 G. BRILL, 3 and N. DHAR 3 1.—Microphysics Laboratory, University of Illinois at Chicago, Chicago, IL 60607. 2.— United States Army RDECOM CERDEC NVESD, Fort Belvoir, VA, 22060. 3.—United States Army Research Laboratory, Adelphi, MD, 20783. 4.— E-mail: junzhao@uic.edu We present results on the surface morphology and recombination lifetimes of molecular-beam epitaxy (MBE)-grown HgCdTe (211)B epilayers and correlate them with the roughness of the CdZnTe substrate surfaces. The substrate surface quality was monitored by in-situ spectroscopic ellipsometry (SE) and reflection high-energy electron diffraction (RHEED). The SE roughness of the substrate was measured after oxide desorption in the growth chamber. The RHEED patterns collected show a strong correlation with the SE roughness. This proves that SE is a valuable CdZnTe prescreening tool. We also found a correlation between the substrate roughness and the epilayer morphologies. They are characterized by a high density of thin elongated defects, “needle defects,” which appear on most samples regardless of growth conditions. The HgCdTe epilayers grown on these substrates were characterized by tempera- ture-dependent, photoconductive decay-lifetime data. Fits to the data indicate the presence of mid-gap recombination centers, which were not removed by 250°C/24-h annealing under a Hg-rich atmosphere. These centers are believed to originate from bulk defects rather than Hg vacancies. We show that Te annealing and CdTe growth on the CdZnTe substrates smooth the surface and lower substantially the density of needle defects. Additionally, a variety of in- terfacial layers were also introduced to reduce the defect density and improve the overall quality of the epilayer, even in the presence of less than perfect sub- strates. Both the perfection of the substrate surface and that of its crystalline structure are essential for the growth of high-quality material. Thus, CdZnTe surface polishing procedures and growth techniques are crucial issues. Key words: Molecular beam epitaxy (MBE), HgCdTe, defects, surface morphology, ellipsometry, reflection high-energy electron diffraction (RHEED) Journal of ELECTRONIC MATERIALS, Vol. 33, No. 8, 2004 Regular Issue Paper 881 (Received September 26, 2003; accepted April 9, 2004) INTRODUCTION High-quality mercury cadmium telluride, suit- able for device applications, is difficult to obtain by either bulk or epitaxial growth. Compared with other material growth techniques, molecular-beam epitaxy (MBE) growth is most suitable for the growth of high-quality complex heterojunctions and multilayer structures for future, infrared focal-plane arrays. One of the challenges posed by the MBE growth of HgCdTe is the understanding and control of visible defects on the surface. The defects observed are of several varieties. 1,2 Some, such as voids and mi- crotwins, are introduced during growth; others are more related to imperfections or substrate prepara- tion procedures. Even though substrate issues for the growth of HgCdTe have been reported previ- ously, 3,4 more studies are needed to fully understand and control substrate-related defects. Here, we present our results on the surface mor- phology of HgCdTe epilayers grown by MBE. These