Properties of Chlorine-Doped Zinc Selenide Grown by Molecular Beam Epitaxy

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PROPERTIES OF CHLORINE-DOPED ZINC SELENIDE GROWN BY MOLECULAR BEAM EPITAXY S. HWANG, J. REN, K.A. BOWERS, J.W. COOK, JR., and J.F. Department of Physics, North Carolina State University, North Carolina 27695-8202

SCHETZINA Raleigh,

ABSTRACT ZnSe:CI epilayers have been grown on (100) GaAs by MBE using a Zn to Se beam flux ratio of 2:1 and substrate temperatures as 0 The ZnSe:Cl epilayers are highly conducting and low as 225 C. A mobility exhibit bright blue-violet edge luminescence at 300 K. 2 of 2480 cm /V-s at 40 K was measured for an n-type ZnSe:CI film 3 17 cmand for which a compensation that was Cl-doped to -2.3x10 Carrier concentrations as ratio (NA/ND) of -3% was calculated. 18 cm- 3 were obtained by increasing the temperature large as 6.7x10 of the MBE oven containing the C1 dopant. INTRODUCTION a wide band gap II-VI semiconductor that has ZnSe is Its room attracted considerable attention in recent years. temperature band gap of - 2.7 eV makes it an attractive candidate [1,2]. for the fabrication of blue light emitting devices Although p-type doping is currently the major obstacle in making such devices, efficient activation of n-type dopants is of equal lasers are to be if semiconductor especially importance, High n-type doping is also required for other related developed. devices such as optical modulators, transistor amplifiers, and diode detectors which might form the basis of a new blue-green Recent investigations by MBE [3] and optoelectronics technology. MOVPE [4] have shown that very high n-type doping levels can be achieved in ZnSe films using group VII elements as dopants. However, the samples reported to date generally exhibit low Hall In spite mobilities compared to n-type ZnSe:Ga doped films [2]. of this, we consider the group VII elements as the most promising In this paper we report the successful MBE growth n-type dopants. The films exhibit of n-type ZnSe:CI films at low temperatures. excellent electrical and optical properties. II.

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The ZnSe:Cl samples were grown in an MBE system designed and The growth built at North Carolina State University (NCSU) [5]. 11 torr and is equipped with chamber has a base pressure of 6x10The MBE sources feature special twoseven MBE sources. designed and constructed at NCSU temperature-zone furnaces, specifically for the growth of II-VI materials, which are capable High purity (6N of producing highly stable beam fluxes (6]. grade) Zn and Se were used as primary source materials, and ultra To dry ZnCI2 (5N grade) was used used as the dopant source. calibrate the molecular beam flux density from each of the primary films were deposited at room temperature and their MBE ovens, The beam flux was calculated assuming thicknesses were measured. unity sticking coefficient and correlated with the beam equivalent measured with a nude ion gauge at the exact pressure (BEP) Both the Zn and Se source beams location of the substrate (5]. Mat. Res. Soc. Symp. Proc. Vol. 161. ©1990 Materials Research Society

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were calibrated in this way so that an