GA OUT-DIFFUSION IN RAPID-THERMAL-PROCESSED GAAS WITH SIO2 ENCAPSULANTS

Effects of rapid thermal processing (RTP) using halogen lamps on GaAs with 50-, 200-, and 1250-nm-thick SiO2 encapsulants have been studied by capacitance-voltage, secondary-ion-mass spectroscopy, and x-ray photoelectron spectroscopy. RTP has been performed at 760 and 910-degrees-C for 9 s. A decrease of the carrier concentration is observed near the SiO2/GaAs interface in all RTP samples. The decreased carrier concentration profile is fitted to a complementary error function diffusion profile. This indicates that the decrease of the carrier concentration by RTP is related to the Ga out-diffusion through SiO2. Furthermore, the amount of the decreased carrier concentration is found to be proportional to the doped Si concentration. These results show that the origin of the carrier concentration decrease is the formation of V(Ga)-Si(Ga) complex defects called the self-activated center. The amount of the Ga out-diffusion is larger in the RTP samples at 760-degrees-C with thicker SiO2 and at 910-degrees-C with a thinner one. This inverse relation can be explained by taking account of two different kinds of driving force, that is, interfacial thermal stress and the interfacial reaction between GaAs and SiO2. Interfacial thermal stress enhances the Ga out-diffusion in RTP at 760-degrees-C, while interfacial reaction enhances in RTP at 910-degrees-C through As loss.