Poly Si1−xGex films have been suggested as a promising alternative to the currently employed poly-Si gate electrode for CMOS technology due to lower resistivity, less boron penetration, and less gate depletion effect than those of poly Si gates. We investigated the formation of poly Si1−xGex films grown by UHV CVD using Si2H6 and GeH4 gases, and studied their microstructures as well as their electrical characteristics. The Ge content of the Si1−xGex films increased linearly with the flux of the GeH4 gas up to x=0.3, and saturated above x=0.45. The deposition rate of the poly Si1−xGex films increased linearly with the flux of the GeH4 gas up to x=0.1, above which it is slightly changed. The resistivity of the Si1−xGex films decreased as the Ge content increased, and was about one half of that of poly-Si films at the Ge content of 45%. The C-V measurements of the MOSCAP structures with poly Si1−xGex gates demonstrated that the flat band voltage of the poly Si1−xGex films was lower than that of poly-Si films by 0.2V.

We report successful application of a low-temperature-grown amorphous GaAs (a-GaAs) layer for stabilization of the fundamental transverse mode of InGaAs/GaAs vertical-cavity surface-emitting lasers. The maximum currents maintaining a stable fundamental transverse mode were increased by the antiguide effect of a-GaAs with a high refractive index. For 10-μm- and 15-μm-diameter devices, we attained a stable single-mode emission over a wide range of current. The antiguiding of transverse modes in vertical cavity buried in the high refractive cladding layer was calculated using a two-dimensional beam propagation method.