ARSENIC DESORPTION FROM THE INAS(001) GROWTH SURFACE DURING ATOMIC LAYER EPITAXY

We report here the importance of suppressing arsenic desorption from the surface of InAs(001) during atomic layer epitaxy (ALE) using trimethylindium (TMIn) and arsine (AsH3) as sources, to achieve an ideal self-limiting monolayer growth. The dependence of the InAs growth rate on the purge time after each reactant flow at growth temperatures from 350 to 400-degrees-C was examined. The growth rate decreased significantly with each increase in hydrogen (H-2) or nitrogen (N2) purge time after exposure to AsH3 until a constant value was reached. The rate was independent of the H-2 purge time after TMIn supply. Ideal monolayer-saturated growth was attained when the purge time after AsH3 was set to less than 0.5 s at 365-degrees-C and to less than 0.1 s at 400-degrees-C. These results indicate that the outermost arsenic atoms desorb from the growth surface after the end of an AsH3 pulse, and that the surface arsenic coverage, which is probably related to surface reconstructed structure, changes to a new steady state determined mainly by growth temperatures. The indium-terminated surface, however, is thermally stable and prevents the desorption of arsenic atoms beneath the surface. We found that accurate control of the purge time after AsH3 supply is very important to InAs ALE and we succeeded in the ideal ALE at a wider range of temperatures, 350 to 400-degrees-C.