Selected area epitaxy in II–VI compounds by laser-induced photo-metalorganic vapor phase epitaxy

Abstract

Selected area epitaxy of CdTe onto GaAs(100)2°→(110) substrates is reported where a frequency-doubled argon ion laser, output wavelength of 257 nm, is used to photolytically decompose the precursors. Photodissociation of the precursors dimethyl telluride, dimethyl ditelluride, diethyl telluride, and dimethyl cadmium have been investigated for their suitability in terms of their ultraviolet absorption spectra and thermal stability. Diethyl telluride or dimethyl telluride have strong absorptions at 257 nm and have good thermal stabilities yielding high photoenhancement factors. Nucleation of CdTe onto GaAs substrates has revealed the need to remove the native oxide for epitaxial growth. HeNe laser thin-film interference has indicated a 4-min nucleation delay for pyrolytic precursor decomposition. Photopatterned CdTe epitaxy has been demonstrated at 300 °C for a two-dimensional mesa pattern obtained by shadow masking and a bar pattern obtained by projection onto the surface. Deposition due to vapor diffusion of Cd and Te was only evident at high laser intensities. At low intensities feature definition is very good with feature sizes ∼100 μm. These results are explained by surface-rate-limiting kinetics that can be stimulated by the laser radiation. Such a mechanism could be laser-stimulated hydrocarbon desorption.