Computational studies of the metalorganic vapor phase epitaxy (MOVPE) of III-V compound semiconductors.

摘要

Although Metalorganic Vapor Phase Epitaxy (MOVPE) has emerged as the most versatile and cost-effective technique for the growth of virtually any compound semiconductor it is still hampered by the lack of ample kinetic information and by excessive experimental trial and error. Detailed reaction-transport models can help in gaining the necessary physicochemical insight and can lead to optimal reactor designs, producing uniform films and abrupt heterojunctions. Furthermore, accurate, low-order dynamic models of MOVPE are essential tools for the development of closed-loop control strategies.; A kinetic model of the MOVPE of InP from trimethyl-indium and phosphine—including gas-phase and surface reactions—was constructed and coupled to a 2-dimensional transport model of the flow, heat and mass transfer in horizontal reactors. Unknown rate parameters were estimated by comparing predicted growth rates with experimental ones. A reduced kinetic mechanism able to accurately predict growth rates, with lower computational cost was extracted through sensitivity analysis and was used in parametric studies of the effects of operating conditions on film growth rates.; The Low-Pressure MOVPE of GaAs from triethyl-gallium and arsine—a precursor combination that produces GaAs films with very low carbon contamination—was also studied. A kinetic model based on reported decomposition mechanisms was developed and coupled to a transport model of an experimental reactor. Finite Element (FEM) simulations were performed to estimate rate parameters of the growth reactions and to investigate the effects of surface chemistry and susceptor temperatures on film growth and uniformity.; Robustness issues of reaction-transport models were addressed. The MOVPE of GaAs from trimethyl-gallium (TMG) and arsine was considered with the objective to construct reactor-independent models. A kinetic mechanism was extracted from reported kinetic studies and the frequency factor of the growth reaction was adjusted to match experimental observations from a rotating-disk (RD) reactor. The model was able to reproduce reported growth rates and uniformities from a horizontal reactor in 2- and 3-D FEM simulations, without further adjustments.; A reaction-transport model of the MOVPE of GaN from TMG and ammonia in stagnation-flow and RD reactors was developed and employed in the design of axisymmetric gas inlets which feed precursors separately into the reactor to eliminate parasitic pre-reactions. FEM simulations were performed to identify designs that can lead to the growth of uniform films over large area substrates.; Finally, a systematic method for order reduction of dynamic MOVPE models was demonstrated. Transients arise in MOVPE due to precursor switching during the growth of heterostructures. The Proper Orthogonal Decomposition (POD) method was employed to obtain accurate reduced models from full-scale FEM dynamic simulations of TMG dispersion in a horizontal MOVPE reactor. Reduced models can be coupled with in-situ probes of the growth and used for on-line, model-based feedback control, which is an essential step towards the realization of a Virtual MOVPE reactor.