Interpretation of Absolute Laser Reflectance During Optical Monitoring of Polycrystalline GaAs Deposition on Quartz Using Metalorganic Chemical Vapor Deposition

Abstract

Gallium arsenide was deposited by metal organic chemical vapor deposition in a horizontal quartz reactor tube using trimethylgallium and arsine at 400 o C -500 o C. Nucleation time and deposition rate were monitored using in situ laser reflectometry. This allowed differentiation between film and parasitic growth, which was not possible with other optical techniques. An absolute reflectance model was developed using measurements prior to GaAs deposition, and then employed to calculate values for GaAs on quartz. Detected reflectance intensities during experimental GaAs deposition were low compared to the model due to 3-dimensional island growth, causing scattering of the incident laser radiation.