NUMERICAL SIMULATION OF THE DEPOSITION PROCESS AND THE EPITAXIAL GROWTH OF CADMIUM TELLURIDE THIN FILM IN A MOCVD REACTOR

Abstract

Metalorganic Chemical Vapour Deposition (MOCVD) is an attractive method for depositing thin films of cadm ium telluride (CdTe) and other group II-VI compound materials. It has been known that the growth rate of CdTe thin film is sen sitive to the substrate temperature and the reactant partial pres sures, indicating that the deposition process is kinetical ly controlled and affected by many conditions. In the deposition process, heterogeneous reactions play an important role in f ilm formation and the process is further complicated by the coupling of gas and surface reactions via desorptio n of the reactive intermediates. A detailed understanding of the deposition mechanism and kinetics will be crucial f or the design, optimization and scale-up of II-VI MOCVD reactors. This paper presents the results of CFD modelling of the deposition process in an inline MOCVD reactor, taki ng into account the heat transfer and mass transport of the chemical species. The numerical simulations have been conducted using the CFD code, ANSYS FLUENT. The influence of the process controlling parameters such as total flow rate, rea ctor pressure and substrate temperature on the deposition behavio ur has been assessed. In the present study, dimethylcadmium (DMCd) and diisopropyltelluride (DiPTe) have been used as prec ursors while H 2 is acting as the carrier gas and N 2 as the flushing gas. The capabilities of using the developed CFD models for revealing the deposition mechanisms in MOCVD have been demonstrated. The simulations have been conducted in both mass transport and kinetics regimes at the temperat ure range of 355-455 ° to match the experimental conditions.