Deposition of Gallium Phosphide on Silicon by Metalorganic Chemical Vapor Deposition

Abstract

This thesis explores the deposition of GaP on GaP (100)-4° and (111)A, and Si (100), (100)-4° and (111) surfaces using metalorganic chemical vapour deposition (MOCVD) for epitaxial growth. The effects of Sb as a surfactant is also investigated. GaP/Si/GaP heterostructures are an ideal candidate for efficient difference frequency generation into the mid-infrared spectrum through engineered quasiphase matched (QPM) templates. The difference in polarity at the GaP/Si interface makes defect-free GaP/Si growth challenging to accomplish, but the minimal lattice mismatch and infrared transparency makes it a promising economical approach to achieve high-speed satellite communication. Developing orientation patterned (OP) templates requires controlling whether primarily Ga-Si or P-Si bonds form at the interface, as these bonds are what dictate the domains orientation. The choice of pre-treatment conditions, growth conditions, and precursor species can affect the interface bonding and twin formation, both crucial factors in developing OP-QPM templates. This work extends previous studies by exploring new experimental conditions and the resulting film morphology. Conditions for smooth GaP surfaces using TMGa and PH3 are found. Heteroepitaxy of GaP on (100) and (100)-4° Si both yielded nano-sized crystallites with a 550 °C pre-treatment and growth, but nanowires under 750 °C pre-treatment. Both yield larger dot-like crystallites under the 750 °C pre-treatment and growth. The GaP/Si(111) surface yields similarly-sized crystallites under the 550 °C pre-treatment and growth conditions, but with significant densities of spiraling nanowires. Under the 750 °C pre-treatment and 550 °C growth, micron-sized crystallites with few nanowires, and larger chain-like clusters form. Sb was found to play a significant role in the low-temperature nucleation on Si (100) and suppression of nanowires on Si (111). These results contribute to the understanding of GaP epitaxial growth by MOCVD and Sb as a surfactant for GaP/Si heterostructures.