Properties of a poly-Si/GaAs layered structure on Si for Si heterojunction bipolar transistor
The properties of poly-Si/GaAs layered films on Si for use in wide bandgap emitters for Si heterojunction bipolar transistors (Si-HBTs), were studied. A smooth GaAs film surface grown on Si was obtained at low temperature (200° C) from the initial stage of growth. The x-ray diffraction (XRD) results indicated that strong GaAs orientation (111) was obtained for the poly-Si/GaAs/Si-substrate layered structure after annealing at 800° C for 20 sec. Secondary ion mass spectroscopy (SIMS) profiles indicated that impurity diffusion from the GaAs layer into the p-type Si substrate was negligible at 800° C. The electrical characteristics forn-poly-Si/n-GaAs/p-Si-substrate heterojunction diodes were also investigated.