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STUDY OF 31B3 ZnSe GROWTH USING RHEED OSCILLATIONS

FRANCOISE S. TURCO AND M.C.TAMARGO BELLCORE, 331 Newman Springs Road,

Red Bank,

NJ 07701

ABSTRACT Reflection high energy electron diffraction (RHEED) intensity oscillations are often used to investigate in situ the growth of III-V materials by molecular beam epitaxy (MBE). In this work, we have used RHEED oscillations to perform a quantitative study of the growth mechanisms of ZnSe, a II-VI semiconductor. Our experiments illustrate that the RHEED pattern of ZnSe is far less intense than that of III-V materials grown by MBE, and no specular spot is observed over a wide range of growth conditions. We have, however, been able to record up to 25 oscillations allowing a quantitative study of the growth of ZnSe by MBE. Thus we have used RHEED oscillations to make an in situ systematic study of the influence of the three main growth parameters (substrate temperature and Zn or Se impinging fluxes) on the ZnSe growth rate. We observed that the variation of the ZnSe growth rate is due to a non unity sticking coefficient of both Zn and Se species at the interface in the standard growth conditions used. Our observations can be described using a thermodynamic model and enable us to control the desired growth conditions. Our work demonstrates the utility of RHEED oscillations to understand the MBE growth mechanisms of II-VI compounds. INTRODUCTION Recently there has been a resurgence of interest in the preparation of ZnSe, a very promising II-VI semiconductor for blue-light emitting devices,[l] as a result of advanced growth techniques such as molecular beam epitaxy (MBE). ZnSe of good quality can now be achieved by MBE. Reflection high energy electron diffraction (RHEED) intensity oscillations have been extensively used to study the growth mechanisms by MBE in situ during III-V compounds growth. Nevertheless, only a few studies have been made of II-VI compounds using the RHEED oscillations technique (ZnSe,(2,3] MnSe,[4] ZnTe [5] or CdTe.(6] Until now, quantitative data concerning the growth mechanisms of ZnSe by MBE have only been obtained by post-growth measurements. RHEED oscillations were reported for the first time in ZnSe by Yao et al [2] and were used to demonstrate the bi-dimensional layer-by-layer growth mode of ZnSe. They have recently been used to characterize the quality of the interface of ZnSe grown on GaAs epilayer,[3] and to accurately measure the growth rate of ZnSe in order to grow ZnSe/MnSe superlattices.[4] In order to make a systematic study of the influence of the three main growth parameters (substrate temperature T and Zn and Se impinging fluxes) on ZnSe epitaxy, we have used in situ measurements of RHEED intensity oscillations. We report in this paper the variation of the incorporation coefficient of Zn versus TS for various II/VI flux ratios. We will use a thermodynamic model to describe the trends observed, as has been Mat. Res. Soc. Symp. Proc. Vol. 145. ©1989 Materials Research Society

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previously done for GaAs MBE by Heckingbottom. [7] We