Surface Reaction Kinetics in Metalorganic Vapor Phase Epitaxy of GaAs through Analyses of Growth Rate Profile in Wide-Gap Selective-Area Growth

Abstract

Wide gap selective area growth was proposed as a probe for obtaining information of surface kinetics in the metalorganic vapor phase epitaxy (MOVPE) of GaAs. GaAs was grown over patterned substrates using a SiO2 mask. The characterized growth-rate enhancement profiles for several total pressures were successfully fitted with two-dimensional simulation, taking only gas phase diffusion into account, except for the profiles in the vicinity of the mask edge, which seemed to reflect surface diffusion. The only parameter governing the profile was D/ks, the ratio of the gas-phase diffusion coefficient (D) to the surface reaction rate constant (ks) of a film precursor. The value of D can be estimated using the Chapman–Enskog kinetic theory, the accuracy of which was validated by observing a reactor-scale growth-rate profile under the mass-transfer-limited regime, and thus we obtained the value of ks. The sticking probability of a precursor, which was converted from ks, ranged between 0.06 and 0.33 for the temperature range of 823 to 973 K. The values are smaller than unity which was often assumed in growth simulations. The value of ks was measured as a function of growth temperature. Its activation energy changed at around 873 K: 8 kJ/mol for higher temperature and 121 kJ/mol for lower temperature. This information is important not only in the design of a selective-area growth process but also for constructing a more realistic reaction model of MOVPE.