Semiclassical Calculation of Reaction Rate Constants for Homolytical Dissociation Reactions of Interest in Organometallic Vapor-Phase Epitaxy (OMVPE)

Abstract

A procedure for calculating homolytic dissociation rate constants is reported for modeling organometallic vapor-phase epitaxy (OMVPE) of III−V compounds for all pressure regimes. Reaction rate constants were predicted following a semiclassical approach based on quantum mechanical calculations and transition-state theory. The critical configuration was determined using linear interpolations for the geometry of the intermediate structures, Morse potentials for the intermediate electronic energies, and Hase's relationship for the vibrational frequencies that become annihilated. Low-pressure rate constants were calculated from Rice−Ramsperger−Kassel−Marcus (RRKM) theory following the Troe approach. The calculations were compared with experimental values for the dissociation of one methyl radical from the closed-shell molecules Al(CH3)3, Ga(CH3)3, and In(CH3)3 and the radical molecules Ga(CH3)2 and In(CH3) and for the dissociation of one hydrogen atom from NH3, PH3, and AsH3. A simplified system of reactions for the homolytic dissociation of In(CH3)3 was modeled in an OMV reactor designed for the pressure range 10-2 to 102 atm using computational fluid dynamics coupled with chemical kinetics. The steady-state simulations were carried out at 1000 K and at N2 pressures of 1 and 20 atm.

The characterization of InN growth under high‐pressure CVD conditions

“…Its surface sensitivity enables the tracking of variations in surface constituents, which can be linked to the evolution of precursor species/fragments in the gas phase. The results of the decomposition dynamics provide the initial basis for a more detailed understanding of the dissociation of the precursors ammonia and TMI and of the reaction rate constants for growth of InN as theoretical predicted by Cardelino et al [31]. The real-time diagnostic tools employed are uniquely suited to follow the growth process with sub-monolayer resolution and to engineer/control the layer quality/properties of indium rich group III-nitrides.…”

“…However, literature data for InN growth by OMCVD indicate a growth temperature of 675 K to 750 K [5], 775 K [29], 810 K-840 K [30]. Under HPCVD conditions, it is possible to increase the growth temperature about 50 K-150 K higher than possible under low-pressure OMCVD conditions [21,31]. However, this may still leave a temperature mismatch between optimum ammonia decomposition and optimal InN growth temperature.…”

Reaction rate of propene pyrolysis

“…This is obviously desirable and convenient in understanding the intrinsic insights of the reactions though a numerical result can be obtained with a kinetics software (e.g., COMSOL35 or KINTECUS36) to solve the coupled differential equations once the rate constants of the elementary reactions are known. Actually, the rate constants for all of the refined34 elementary reactions can be found in references 37–49. Nevertheless, some inconsistencies were found and will be discussed in more detail.…”

Real-time optical monitoring of gas phase dynamics for the growth of InN at elevated pressures

“…Based on the result of flow simulations [9][10][11] a flow channel reactor geometry as depicted in Fig. Based on the result of flow simulations [9][10][11] a flow channel reactor geometry as depicted in Fig.…”

“…In order to gain insights in the growth dynamics under elevated pressures, we designed and constructed a high-pressure flow channel reactor system for the growth of group III-nitrides that incorporates real time optical characterization capabilities [9][10][11][12]. At higher pressures, only optical diagnostic techniques can provide real time information pertaining to gas flow dynamics, allowing the characterization of laminar and turbulent flow regimes.…”