Interrupted cycle chemical beam epitaxy of gallium phosphide on silicon with or without photon assistance

The low temperature epitaxial growth of Si-GaP heterostructures by chemical beam epitaxy (CBE) and interrupted cycle chemical beam epitaxy (ICCBE) on patterned partially SiO2 masked silicon substrates is investigated to achieve dielectric isolation layers for Si circuits as well as for optical interconnections. Excellent selectivity of the growth on exposed Si windows versus SiO2 covered surface areas is observed and verified by Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). Low temperature processing is essential to minimize interdiffusion and strain due to substantial mismatch of the thermal expansion coefficients of GaP and Si. We describe the deposition of GaP by CBE and ICCBE using sources of tertiarybutylphosphine (TBP) and triethylgallium (TEG) on (100) silicon at 310°C and the influence of photon assistance on the growth temperature and surface morphology. Secondary ion mass spectroscopy (SIMS) studies reveal that no measurable interdiffusion occurs under these conditions, including subsequent processing steps that require rapid thermal annealing for 30 s at 900°C. The GaP/Si interface is examined by high resolution cross-sectional transmission electron microscopy (HRTEM) before and after the 900°C anneal.