MOVPE growth of MgSe and ZnMgSe on (100)GaAs

We report on the MOVPE of MgSe and ZnMgSe on (100)GaAs. Dimethylzinc:triethylammine, ditertiarylbutylselenide and bis(methylcyclopentadienyl)magnesium were used as Zn, Se and Mg sources, respectively. MgSe and ZnMgSe layers were grown either directly on GaAs or after a thin pseudomorphic ZnSe layer. To avoid the hygroscopicity of Mg-based chalcogenides, a ZnSe capping layer was grown on some samples. The crystallographic phase of as-grown layers was determined by both single- and double-crystal X-ray diffraction measurements. MgSe layers turned out to be mosaics made of (1 1 1)- and (1 0 0)-oriented 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/(100)GaAs in the ZB phase. The MOVPE solid/vapour distribution curve of ZnMgSe is presented, showing that the incorporation of Mg 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 dimethylzinc. 5K cathodoluminescence measurements performed on ZnMgSe showed dominant deep blue near band-edge emission which shifts towards higher energies by increasing the amount of Mg. Weak self-activated bands were also observed in the spectra.