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STUDY OF HgTe-CdTe MULTILAYER STRUCTURES BY TRANSMISSION ELECTRON MICROSCOPY N. OTSUKA and Y. E. IHM School of Materials Enqineering Purdue University, W. Lafayette,

IN 47907

K. A. HARRIS, J. W. COOK, Jr., and J. F. SCHETZINA Department of Physics, N. Carolina State University Raleigh, NC 27695-8202 ABSTRACT A transmission electron microscope study of HqTe-CdTe multilayer structures grown by molecular beam eoitaxy (MBE) on (100) Cd Zn Te is presented. Both cross-sectional and plain-view 160er~ations show highly reaular structures of superlattices and tunnel structures. Dislocation densities estimated by Plan-view observations are of the order of lO4 cm in these multilayer structures. A quantitative characterization of interface sharpness of superlattices has been carried out by intensity analysis of satellite spots in electron diffraction patterns. It is shown that interfaces in these superlattices are hichly abrupt with a width of one or two monolayers. These observations suggest the effectiveness of the use of lattice-matched substrates to qrow high quality HgTe-CdTe multilayer structures. 1. Introduction Since the first qrowth of HgTe-CdTe superlattices [1], molecular beam epitaxy (MBE) has become a leading growth technique of Hg-based multilayer structures. A variety of novel multilayer structures of Hg-based materials have been grown by this technique, stimulatina intensive experimental and theoretical studies for the development of oDtoelectronic devices of these structures. At Present, two materials, GaAs and Cd, Zn Te (CdTe), are primarily used as substrates for the gr wh •f Hg-based materials by MBE. GaAs is widely used because of the availability of high quality crystalline surfaces and the possibility of the monolithically integrating technology of Hg-based structures with that of GaAs. Recently, however, Cd Zn Te is increasingly becoming an attractive substrate b~cus6 of its lattice-matchinq with HgTe, and many high quality HaTe-CdTe multilayer structures have been successfully grown on this substrate [2,3]. In this Paper, we present a transmission electron microscope (TEM) study of HgTe-CdTe multilayer structures qrown on Cd Zn Te substrates by MBE. Two aspects of microstructures,-lisfocation densities and interface sharpness have been primarily investigated in the study. 2. ExPeriment Hg-based multilayer structures were grown in a MBE system specially designed for the growth of these materials. Film growth was carried out at 175'C on (100) CdTe or (100) Mat. Res. Soc. Symp. Proc. Vol. 90. ý 1987 Materals Research Society

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Zn Te substrates with a deposition rate of 1-2 A/sec. Cd growth procedures are described in earlier reports Delafle [2,4]. Cross-sectional and plan-view specimens for TEM studies were prepared by mechanical grinding followed by Ar ion milling. A JEM 200CX electron microscope with a side-entry goniometer was used for TEM observations. 3. Results and Discussion Figure 1 (a) and (b) are bright field images of HgTeCdTe superlattices. The area shown in Fig.l(a) represents a typica