MOVPE growth of MgSe and ZnMgSe on (100)GaAs

We report on the MOVPE of MgSe and ZnMgSe on (100)GaAs. Dimethylzinc:trieth ylammine, ditertiarylbutylselenide and bis(methylcyclopentadienyl)magnesium were used as Zn, Se and Mg sources, respectively. MgSe and ZnMgSe layers w ere grown either directly on GaAs or after a thin pseudomorphic ZnSe layer. To avoid the hygroscopicity of Mg-based chalcogenides, a ZnSe capping laye r was grown on some samples. The crystallographic phase of as-grown Layers was determined by both single- and double-crystal X-ray diffraction measure ments. MgSe layers turned out to be mosaics made of (1 1 1)- and(1 0 0)-ori ented MgSe crystals in their rocksalt phase. No signatures of the zincblend (ZB) phase was observed, irrespective of whether MgSe was grown on (1 0 0) GaAs or after the ZnSe buffer. Zn1-xMgxSe (0.07 < x < 0.45) epilayers were grown on ZnSe/(1 DO)GaAs in the ZB phase. The MOVPE solid/vapour distributi on curve of ZnMgSe is presented, showing that the incorporation of ME into the ternary crystal is less efficient than Zn, a result of the smaller gas phase diffusion coefficient: of the Mg alkyl with respect to that of dimeth ylzinc, Five Kelvin cathodoluminescence measurements performed on ZnMgSe sh owed dominant deep blue near band-edge emission which shifts towards higher energies by increasing the amount of Mg. Weak self-activated bands were al so observed in the spectra. (C) 2000 Elsevier Science B.V. All rights reser ved.