New allyl selenide and trialkylphosphine selenide precursors for metalorganic vapor phase epitaxy of ZnSe

Abstract

New allyl selenide and trialkylphosphine selenide reagents; specifically, t-butylallyl selenide (tBASe) and tripropylphosphine selenide, are described for the metalorganic vapor phase epitaxy (MOVPE) of ZnSe. The gas-phase chemistry of allyl selenide precursors is discussed, with emphasis on reactions leading to carbon incorporation. Secondary ion mass spectrometry shows a negligible carbon incorporation in ZnSe films grown from tBASe even at high [VI]/[II] ratios, in contrast to a carbon concentration of 10 21 cm −3 in ZnSe films grown from diallyl selenide and methyl allyl selenide. The low carbon concentration is attributed to the t-butyl group precluding internal rearrangement reactions responsible for carbon incorporation. Low temperature growth and short residence times are critical to minimizing alkyl group redistribution reactions that lead to formation of potential carbon precursors; specifically, diallyl selenide. Good surface morphology on (001) GaAs and photoluminescence spectra with sharp near-band-edge excitonic emission is reported. The need to reduce hydrogen incorporation to improve nitrogen doping characteristics motivates the development of alternative Se precursors circumventing formation of Se-H moieties. Phosphine selenides are proposed as a promising family of reagents and results are presented for growth of ZnSe with tripropylphosphine selenide and dimethylzinc.