Journal of Crystal Growth 95 (1989) 533-537 533 North-Holland, Amsterdam INCORPORATION PROCESSES IN MBE GROWTH OF ZnSe R. VENKATASUBRAMANIAN School of Electrical Engineering, Purdue University, West Lafayette, Indiana 47907, USA N. OTSUKA School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, USA and J. QIU, L.A. KOLODZIEJSKI and R.L. GUNSHOR School of Electrical Engineering, Purdue University, West Lafayette, Indiana 47907, USA Absolute measurements of Zn and Sc fluxes employed in MBE growth of ZnSe have been performed by using three different methods, the deposition of Zn or Se on cold substrates, the estimation by a crystal monitor, and the growth of ZnSe under the Zn or Se over-flux conditions. Based on the results of the flux measurements, the flux ratio was set at unity in the growth of (100) ZnSe at 3200 C. Under this condition, the growth surface exhibits a (2 x 1) structure, and high sticking coefficients of Zn and Sc were obtained. A model of incorporation processes of Zn and Se in MBE growth of (100) ZnSe is proposed. In recent years, major efforts of molecular beam mum growth condition. In the experiments men- epitaxy (MBE) of ZnSe are directed to the growth tioned above (except those by Yao et al. [1]), beam of low resistivity p-type epilayers. One of the main pressures of Zn and Se fluxes were measured by requirements in achieving this goal is the growth means of an ionization gauge, and the ratio of of stoichiometric epilayers which have sufficiently beam pressures was used as a substitute for the low concentrations of native defects for the con- actual flux ratio, which is defined as the ratio of trolled doping. Although the condition for the numbers of Zn and Se atoms impinging on the growth of high quality single crystalline ZnSe has unit area of a substrate for the unit period of time. been fairly well established to date, the condition In general, a beam pressure ratio determined by for the growth of highly stoichimetnc epilayers an ionization gauge does not coincide with a flux has not been closely investigated. Stoichiometry of ratio because of different relative sensitivities of epilayers is considered to be most directly affected atoms and molecules to ionization. In this case, by the ratio of Zn and Se fluxes among a number particularly, it is extremely difficult to relate a of growth parameters in MBE of ZnSe. In an beam pressure ratio to a flux ratio due to the earlier study [1], Yao et a!. have investigated the evaporation of various forms of molecules from an dependence of the growth rate of (100) ZnSe on elemental Se source [5]. the flux ratio. Recently, Menda et al. [2], DePuydt In the present study, we have made absolute et al. [3], and Cornelissen et al. [4] have studied measurements of Zn and Se fluxes by employing surface structures of (100) epilayers by reflection three different methods. The first method is the high energy electron diffraction (RHEED) for measurement of thicknesses of Zn or Se layers various flux ratios and growth temperatures. Based deposited on cold substrates. The second method on these observations, they have made surface is the growth of ZnSe epilayers under Zn over-flux phase diagrams in order to search for the opti- or Se over-flux conditions; from the thicknesses of 0022-0248/89/$03.50 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)