Dimethyldiselenide and diethyldisulphide as novel Se and S precursors for the low-temperature MOVPE growth of ZnSe, ZnS and ZnSSe

The low-temperature pyrolytic MOVPE growth of ZnSe, ZnS and ZnSxSe1-x is reported by using a novel class of VI-group precursors of the form R2X2 (where X = S, Se and R = ethyl, methyl) along with dimethylzinc : triethylammine. Dimethyldiselenide and diethyldisulphide allow the growth below 400 degrees C, i.e. at temperatures reduced by similar to 150 degrees C with respect to alkyls of the form R2X. The lower thermal stability of these novel precursors is ascribed to a weakening of the X-C bonds in the R,X, molecule induced by the stronger X-X bond. ZnSe and ZnS growth is thermally activated at low temperatures, the activation energies of both processes being around 29.7 kcal/mol. H was detected in undoped ZnSe at concentrations around (1-3) x 10(17) cm(-3), along with unintentional N ranging between 8.6 x 10(16) and 1.4 x 10(18) cm(-3) Cl and I were also present at around 6 x 10(15) cm(-3) and less than or equal to 1 x 10(15) cm(-3), respectively. 10 K cathodoluminescence (CL) spectra of ZnSe and ZnS show both near-band edge and deep centre emissions, but in the CL spectra of thin ZnSe samples the Y-0-line dominates, a clear signature that dislocations occur into these layers. (C) 2000 Elsevier Science B.V. All rights reserved.