LOW-TEMPERATURE CHEMICAL BEAM EPITAXY OF GALLIUM PHOSPHIDE SILICON HETEROSTRUCTURES/

The low temperature epitaxial growth of GaP on (001) Si by chemical be am epitaxy (CBE) was investigated with the aim of usine GaP epilayers for the dielectric isolation of silicon circuits. Optimum CBE of GaP o n silicon, using t-butyl phosphine (TBP) and triethylgallium (TEG) as source vapors, is obtained at 310 degrees C. GaP nucleates on silicon highly selectively with regard to deliberately SiO, and SiC coated sur face regions. This behavior is due to the higher catalytic activity of the GaP surface compared with a silicon dioxide surface with regard t o TBP pyrolysis. The efficiencies of incorporating phosphorus and gall ium at the GaP surface are substantially different and require flux ra tios R(TBP:TEG) greater than or equal to 25 for stoichiometric GaP dep osition. Atomic force microscopy reveals a typical surface roughness o f 75 Angstrom for a film thickness of 2000 Angstrom the GaP growth occ urs initially without interfacial reactions, upon prolonged growth (la yer thickness more than 300 Angstrom) transport of oxygen and carbon t hrough the GaP film to the GaP-Si interface results in the growth of a n SiO2/SiC layer between the silicon substrate and the GaP film, which is desirable in the context of dielectric isolation but requires modi fications of the growth conditions in the context of opto-electronics.