MOLECULAR-BEAM EPITAXIAL-GROWTH OF ALXGA1-XAS (X = 0.2-0.7) ON (111)B-GAAS USING AS4 AND AS2

Basic properties of AlxGa1-xAs (x = 0.2-0.7), grown by molecular beam epitaxy on 0.5-degrees-tilted (111) B-GaAs, are studied. We have employed the wide substrate temperature, T(s), range of 540-740-degrees-C and different As species; As4 and As2. The surface morphology has been found to depend strongly upon the As species; a specular surface morphology cannot be obtained when using As2 whereas a specular smooth surface can be obtained at high temperatures when using As4. Photoluminescence intensity of n-Al0.3Ga0.7As (Si = 1 X 10(18) cm-3) grown at low T(s) (< 620-630-degrees-C) does not depend upon the As species and is considered to be determined by defects, such as microtwins and stacking faults, which have been observed by transmission electron microscopy. At high T(s) (> 650-degrees-C) photoluminescence intensity is lower for the case of As2 than As4 and this could be due to point defects, such as As interstitials and/or antisite As (As(Ga)). Deep level transient spectroscopy has been measured on n-Al0.7Ga0.3As grown on (100)- and (111)B-substrates with As4.