Microscopic analysis on surface reaction induced by laser irradiation and its application to atomic layr epitaxy

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Control of GaP growth at the atomic-layr level has been achieved by laser-triggering in metalorganic molecular beam epitaxy (MOMBE) under a simultaneous supply of triethylgallium and thermally cracked PH_3. The growth rate of GaP was enhanced at low substrate temperatures by ultraviolet light emitted from a N_2 laser. The growth rate is controlled by either the TEGa supply between laser pulses or the photon number, and it shows saturation with a high TEGa supply. This suggests that the adsorption of TEGa on a surface saturates.Surface reactions triggered by pulsed laser irradiation for GaP growth were studied with reflection high-energy electron diffraction (RHEED) at a low temperature of 350ﾟC IN MOMBE.On the laser irradiation, the intensity of RHEED showed an abrupt decrease followed by gradual recovery. The abrupt decrease indicates that adsorbed TEGa on a GaP surface is photo-decomposed by the laser irradiation. The intensity recovery had much dependence on PH_3 flow rate, which indicates that the intensity recovery is related with surface reaction between photo-decomposed TEGa and P atoms. This result shows that the decomposition of TEGa by laser irradiation and the formation of GaP occur alternately under continuous supply of source geses. This opens up a new mode of ALE triggered by laser irradiation without alternate supply of source gases.