ARSENIC-FREE GAAS SUBSTRATE PREPARATION AND DIRECT GROWTH OF GAAS ALGAAS MULTIPLE-QUANTUM-WELL WITHOUT BUFFER LAYER/

High-temperature treatment of GaAs substrate without As flux in a prep aration chamber was investigated as a substrate surface cleaning metho d for molecular beam epitaxial (MBE) growth. Oxide gases such as CO an d CO2 were almost completely desorbed at a temperature above which Ga and As started to evaporate from the substrate. During the cleaning at a temperature as high as 575 degrees C for 30 min, about 100 nm thick GaAs was evaporated from the substrate, but its surface maintained mi rror-like smoothness and showed streak pattern with surface reconstruc tion pattern in the reflection high energy electron diffraction (RHEED ) observation. Direct growth of GaAs/Al GaAs quantum well (QW) structu res was tried on such surfaces without introducing any buffer layers. The QW structure showed photoluminescence with both intensity and full width at half maximum comparable with those for the QW grown on the s ubstrate cleaned by the conventional method with introducing a GaAs bu ffer layer.