VERY-LOW DEFECT DENSITY ZNSE GROWN ON GAAS BY ATMOSPHERIC-PRESSURE METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION

Very low defect density ZnSe epilayers on GaAs substrates have been gr own by metal-organic chemical vapor deposition (MOCVD) and the layers were characterized by various techniques. ZnSe epilayers were grown us ing diethylzinc (DEZn) and diethylselenide (DESe) as source materials. Growth studies were done at 400 degrees C under a Se-started growth c ondition in an atmospheric pressure MOCVD reactor. Different GaAs subs trates were used to study the effect of substrates on the ZnSe quality . The as-grown ZnSe epilayers were characterized by double crystal X-r ay diffraction, transmission electron microscopy (TEM), and scanning e lectron microscopy. The results show excellent surface morphology and crystal quality for ZnSe. The best material was grown on undoped GaAs. A full-width-at-half-maximum (FWHM) of the ZnSe (approximate to 0.2 m u m thick) X-ray peak as low as 90 arc s was achieved. TEM results sho w that ZnSe epilayers grown on undoped GaAs have a very low stacking f ault density acid a large spacing between misfit dislocations. The den sity of the stacking faults is less than 10(5) cm(-2), which is more t han three orders of magnitude lower than that of samples grown by conv entional molecular beam epitaxy [J. Petruzzello et al., J. Appl. Phys. , 63(1988) 2299] and MOCVD [J.L. Batstone et al., Philos. Mag. A, 66(1 992) 609]. The spacing between misfit dislocations is between 5 and 10 mu m, which is 10-20 times that of reported samples of comparable thi ckness.