Heteroepitaxy and properties of III-V materials grown on nanoscopically roughened (001) silicon

The objectives of this work are (1) to study the growth mechanisms of GaP on Si by organometallic chemical vapor deposition (OMCVD) using trimethylgallium (TMG) and phosphine (PH3) as precursors, and (2) to improve the GaP growth quality by using nanoscopically roughened Si substrates. We study the growth comparatively on (001) GaAs and thermally generated SiO2. Inadvertent indirect but important data are also obtained from the polycrystalline GaP deposited on the Mo susceptor surrounding the 2 in. wafers. We use spectroscopic polarimetry (SP) to follow growth in real time, and then analyze the films with atomic force microscopy (AFM) and spectroscopic ellipsometry (SE).;We investigated the gas-phase kinetics inside our vertical-flow, low-pressure OMCVD reactor chamber by calculating various kinetics parameters and characteristic dimensionless numbers based on simple hard-sphere approximations. The results allow a quantitative understanding of the OMCVD processes and the design of optimized growth conditions.;We found that the thicknesses of the deposited GaP films increases or decreases exponentially toward the edge of the wafers. This dependence is incompatible with the common explanation of gas-phase depletion of the precursors. Starting with the diffusion equation, we derive analytic expressions that describe the thickness variations in terms of the diffusion parameters, and evaluate the diffusion length quantitatively. We show that the cause is due to differences in chemical reactivities of the various surfaces, especially the different catalytic effects that they exert on PH3 decomposition. The results also show that different parts of the surface, including the susceptor, are in constant contact with each other during growth through gas-phase diffusion, and that deposition occurs via a precursor that involves both Ga and P and is formed by heterogeneous catalysis.;We proposed a model for the growth of GaP based on the formation of this precursor and the effects of substrate. Our model, when used together with the thermodynamics and kinetic theories of nucleation and epitaxy, provides a consistent explanation of the various growth behaviors that we have observed.