Characterization of HgCdTe Epilayers and HgTe-CdTe Superlattice Structures Grown by Molecular Beam Epitaxy
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Characterization of HgCdTe Epilayers and HgTe-CdTe Superlattice Structures Grown by Molecular Beam Epitaxy
T.H. Myers', R.W. Yanka*, J.P. Karins''K.A. Harris'', J.W. Cook'', and J.F.Schetzina'* *Electronics Laboratory, General Electric Company Syracuse, New York 13221 " North Carolina State University, Raleigh, North Carolina 27695
ABSTRACT The results of an in-depth study of HgCdTe epilayers and HgTe-CdTe superlattice structures are summarized. In particular, both spectral and transient photoconductance measurements have been made on samples which were also characterized by x-ray diffraction, Hall, IR transmission, IR photoluminescence, and transmission electron microscopy measurements. Selected HgCdTe samples grown at General Electric during this investigation exhibit some of the best structural and electrical properties reported to date for MBE-grown HgCdTe. Sharp photoconductance spectra have been obtained for HgTe-CdTe superlattice structures grown at North Carolina State University. This study is part of an on-going collaborative effort between General Electric's Electronics Laboratory and North Carolina State University.
INTRODUCTION
The growth of HgCdTe epilayers and HgTe-CdTe superlattice structures
by molecular beam epitaxy (MBE) is of considerable interest due to the potential use of such materials in infrared detector applications. Superlattice structures, in particular, have been the subject of much attention in recent years because of the interesting properties which they exhibit. For example, the electrical and optical properties of such structures can be modified through proper choice of layer thicknesses and materials -- a form of "band gap engineering". The MBE technique, with its slow, controlled deposition rates and low growth temperatures, offers the best possibility for synthesizing Hg-based layered structures with sharp interfaces such as HgCdTe heterojunctions and HgTe-CdTe superlattices. In this paper, the results of an in-depth study of HgCdTe epilayers and HgTe-CdTe superlattice structures are summarized. In particular, both spectral and transient photoconductance measurements have been made on samples which were also characterized by x-ray diffraction, Hall, IR transmission, IR photoluminescence, and transmission electron microscopy measurements. This study is part of an on-going collaborative effort between General Electric's Electronics Laboratory and North Carolina State University.
Mat. Res. Soc. Symp. Proc. Vol. 90- c1987 Materials Research Society
296
EXPERIMENTAL DETAILS
The epilayers and superlattices were prepared at General Electric's Electronics Laboratory (GE) and at North Carolina State University (NCSU) utilizing MBE systems designed and built specifically for growing Hg-based films and multilayer structures. The system has been extensively described elsewhere [1]. Hg1 -,Cd 0 Te epilayers were grown on (1OO)Cd 0 . 9 6 Zn0 . 0 4Te, (lll)Cd0. 9 6 Zn0. 0 4 Te and (100)CdTe substrates. The substrates were chemimechanically polished on both sides and etched in a Br-met
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