IN-SITU OBSERVATION OF GAAS SELECTIVE EPITAXY ON GAAS (111)B SUBSTRATES

Selective area epitaxy has been carried out by mu-RHEED (reflection high energy electron diffraction)/SEM (scanning electron microscopy) MBE (molecular beam epitaxy) on (111)B patterned substrates masked by SiO2 and conditions for selective growth have been determined as a function of substrate temperature and Ga beam intensity. Below the critical Ga flux, a smooth epitaxial layer grows without any deposition of polycrystals on the masked area. However, in the high temperature region (over 660 degrees C), the epilayer grown in the window is rather rough, due to the high re-evaporation rate of Ga atoms. In the high Ga flux region, polycrystalline deposition on the mask occurs and the coverage of the masked area by poly-GaAs nuclei decreases from the region close to the window to the center of the mask. It has been found that there is a strong lateral surface flow of Ga atoms from the window to the mask region.