Low pressure MOVPE growth and structural properties of ZnMgSe epilayers on(100)GaAs

The low-pressure MOVPE growth of ZnMgSe on (1 0 0)GaAs is reported. ZnMgSe alloys were deposited after a thin pseudomorphic ZnSe buffer layer by using dimethylzinc: triethylammine (Me2Zn:Et3N), ditertiarylbutilselenide (Bu-t( 2) Se) and bis(methylcyclopentadienyl)magnesium [(MeCp)(2)Mg]. Zn1-xMgxSe ( 0.10 <x < 0.46) epilayers were grown at 330 degreesC, 304 mbar and a high V I/II ratio in the vapour. Under these conditions the growth is limited by t he mass transport of the II-group alkyls and good control of the compositio n was achieved. Rutherford backscattering spectrometry measurements allowed to determine the epilayer stoichiometry and deposited dose. The ZnMgSe sol id-vapour distribution curve deviates from linearity due to the different M g and Zn alkyl vapour diffusion coefficients, whose ratio turns out to be D -(MeCp)2Mg/D-Me2Zn = 0.410. The epilayer crystalline properties were studie d by double-crystal X-ray diffraction (DC-XRD) and high-resolution reciproc al space mapping (RSM) measurements. Rocking curve FWHM values of 540-900 n m thick Zn1-xMgxSe were in the 5-12 mrad range, indicating the occurrence o f extended defects in the epilayers. RSM measurements in the vicinity of th e (400)-peak of a Zn0.844Mg0.156 Se/ZnSe(100)GaAs sample showed a slight as ymmetry of the ternary alloy peak along the growth direction, ascribed to a n inhomogeneous relaxation of the epilayer. (C) 2000 Elsevier Science B.V. All rights reserved.