Numerical simulation and analytical models for thin film CdTe layers deposited by an inline AP-metalorganic chemical vapour deposition process

Abstract

The metalorganic chemical vapour deposition (MOCVD) as an attractive method for depositing CdTe and other group II-VI compound thin films has been widely used for fabrication of optoelectronic devices, including photovoltaic solar cells. The thin film deposition of CdTe layer on a substrate with dimethylcadmium (DMCd) and diisopropyltelluride (DIPTe) as precursors has been investigated both numerically and experimentally using an inline reactor. The present work mainly focuses on two aspects of the inline AP-MOCVD process: (1) effects of key deposition parameters such as the substrate temperature Ts, the deposition profile, the film thickness distribution and material utilisation on the pyrolysis of CdTe using the dynamic mode (moving substrate) in the simulation; (2) optimisation of the process conditions using static mode (stationary substrate). Both two-dimension (2D) and three-dimension (3D) computational fluid dynamics (CFD) modelling simulations were conducted to simulate the deposition process. Two modelling modes were trialled in the present work, one with the 2D simulation and optimisation of process conditions being conducted by adopting the dynamic mode and the other with 3D simulation but adopting the static mode. The use of dynamic mode in the CFD modelling for CdTe thin film MOCVD was found to be more suitable for approximation of the actual deposition process. The predicted thin film growth rates are consistent with those obtained from the deposition experiments.