Optical second harmonic generation as an in-situ surface diagnostic probe of semiconductor growth processes. I. Adsorption of triethylgallium on GaAs (100) at 300 K

A preliminary report of the application of the technique of optical second harmonic generation (SHG) to the study of surface chemical processes relevant to semiconductor growth is presented. It is demonstrated that SHG is observed from a GaAs (100) substrate illuminated with primary laser radiation pulses at 1064 nm from an Nd: YAG laser. The SH signal is easily detectable and varies dramatically with time of exposure to triethylgalium at 300 K, implying that the varying portion of the signal stems largely from interactions at the substrate surface. This surface-specificity may be due to (i), the magnitude of the non-linear susceptibility of the resulting adlayer or (ii), a surface resonance-enhancement of the SH signal. It is shown that the dynamic adsorption of triethylgallium on GaAs (100) at 300 K gives rise to a permanent increase in SHG, which by comparison with other systems is suggestive of a dissociative adsorption mechanism.