IN-SITU OBSERVATION OF GA ADSORPTION DURING TMGA EXPOSURE ON GAAS(001) SURFACES WITH VARIOUS AS COVERAGES

We measured transients of surface photoabsorption signals during TMGa exposure on c(4 x 4)-like, 2 x 4-like and Ga-terminated GaAs(001) surfaces in the MOCVD reactor. Ga-containing species were continuously deposited during TMGa exposure on Ga-terminated surfaces. On the other hand, self-limiting deposition was observed on c(4 x 4)-like and 2 x 4-like surfaces. The growth thickness in one cycle of ALE process on the 2 x 4-like surface was 0.7-0.8 compared to that on the c(4 x 4)-like surface. The stable duration of the SPA signal under TMGa exposure was longer than the residency time of methyl groups on the surface which was obtained from the transients during purge after TMGa exposure. Hence the methyl groups are continuously supplied to the surface by decomposition of TMGa during the exposure period under self-limiting condition.