GROWTH OF MGTE AND ZN1-XMGXTE THIN-FILMS BY METALORGANIC VAPOR-PHASE EPITAXY

We report for the first time on metalorganic vapour phase epitaxial (MOVPE) growth of the large band gap semiconductor MgTe and the variable band gap ternary alloy Zn1-xMgxTe. We chose the precursors diisopropyltellurium (DIPTe), diethylzinc (DEZn) and bis-methylcyclopentadienylmagnesium (MCP2Mg). All layers were grown on semi-insulating (100) GaAs substrates in an experimental reactor cell with downflow on a graphite susceptor placed in the centre of a cylindrical vertical tube. The feasibility of growing cubic Zn1-xMgxTe by MOVPE has been demonstrated. The usual optimization of the growth parameters (temperature, inlet partial pressure, growth rate) should result in better optical quality of the material. However, an easy control of the composition is possible with the selected precursors. The composition of the layer versus the inlet partial pressure ratio of the alkyls pMg/ (pMg+pZn) is presented. One observes an overproportional incorporation of the Mg in the layers. It is not yet clear whether this behaviour stems from the low thermal stability of the MCP2Mg compared to DEZn, or whether the thermodynamics of the solid solution influences the composition. Photoluminescence measurements exhibit a deep emission in the green region.