A Multiscale Simulation Approach for the MOCVD of GaN Using a Single‐Molecule Precursor in a Vertical Stagnation Flow Reactor

Abstract

A multiscale simulation approach, including atomistic quantum mechanical calculations on the molecular scale and physical continuum mechanical process simulations on the macroscopic scale, has been used to study the initial gas-phase decomposition of a single-molecule precursor. The compound bisazido(dimethylaminopropyl)gallium (BAZIGA), that forms gallium nitride in the absence of other nitrogen sources, is proposed to decompose by a multistep reaction mechanism to the key intermediate, GaN 3 . The reaction rates for the effective overall reaction were derived on the basis of transition state theory in an ab initio fashion from the results of density functional theory-type calculations. Methods to accurately approximate the entropic contributions to the free energies of activation for the elementary steps were developed and employed. The calculated rates were fit to an Arrhenius type rate law with an apparent energy of activation of E a = 321 kJ mol ±1 (A= 9.9010 20 s ±1 ). Process simulations were performed for a real vertical stagnation flow test reactor. The inclusion of radiative heat transfer was found to be crucial to reproduce the experimentally determined temperature distribution on the reactor wall. By inclusion of the gas phase decomposition to GaN 3 in terms of an effective one-step reaction, only the intermediate GaN 3 was found to contribute to film growth. It is concluded that all parent precursor molecules decompose in the hot zone above the substrate and do not reach the surface under the given conditions.

Thermodynamic Stability of Small GanNn Clusters as Intermediates in GaN CVD

“…In addition, radical reaction steps as proposed by us [21] and others [15] should be taken into account for the formation of these species, and so we are currently investigating the decomposition mechanism of a single-molecule precursor system in detail. [11] 88 www.cvd-journal.de …”

“…We note, however, that increasing the size (n) of the Ga n N n cluster lowers its energy significantly with respect to the Ga (gas) + N 2 system. In our recent study [11] on the decomposition pathway of a very attractive single-molecule precursor [12] for the CVD of gallium nitride, we argued that the GaN 3 species is the only stable source of nitrogen for GaN film growth. The monoazide GaN 3 has, in fact, been found in a matrix isolation study from the quenched gas phase during decomposition of this single-molecule precursor.…”

Multi-scale modeling of chemical vapor deposition processes for thin film technology

“…Most of these studies addressed classical reactor configurations (see Fig. 4), such as horizontal rectangular duct reactors [14,[76][77][78][79][80][81][82], vertical impinging jet and rotating disk reactors [22,[83][84][85][86][87][88], pancake reactors [89,90], barrel reactors [91][92][93], planetary reactors [94][95][96], hot-wall multi-wafer LPCVD reactors [74,[97][98][99]. Many studies were devoted to low pressure single wafer reactors of the stagnation flow type [21,28,[100][101][102].…”