OPTIMIZATION OF PRE-EPITAXIAL PROCESSES TO OBTAIN HIGH-QUALITY ZNSE GAAS HETEROINTERFACES GROWN IN A LOW-PRESSURE METALORGANIC VAPOR-PHASE EPITAXY SYSTEM/

The effect of different surface treatments of GaAs substrates on the s tructural and optical properties of ZnSe were studied for metalorganic vapour-phase epitaxy (MOVPE). Especially, the correlation of the chem ical etching process prior to the growth and surface stabilisation of GaAs either with Zn or Se precursors or an exposure to a DC-hydrogen p lasma was analysed. The precursor combination of ditertiarybutylseleni de (DTBSe) and dimethylzinc-triethylamine (DMZn(TEN)) was used to grow 100 nm thick ZnSe layers at 330 degrees C which are thinner than the reported critical thickness. The characterisation of the layers was ca rried out by double-crystal X-ray diffraction (DCXRD), photoluminescen ce spectroscopy (PL) and cathodoluminescence (CL). In addition, other methods like scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) or atomic force microscopy (AFM) were perf ormed to study the surface morphology. Optimised results were achieved with H2SO4 and HF etching steps in addition with a DTBSe stabilisatio n of the substrates. An 8 min long stabilisation leads to a full-width at half-maximum of 158 '' of (4 0 0) rocking curves for a 93 nm thick ZnSe sample. Moreover, in the PL spectra dominating excitonic emissio n and weak deep centre emissions are observed. (C) 1998 Elsevier Scien ce B.V. All rights reserved.