GaAs photoconductors for submillimeter astronomy: liquid phase epitaxial growth of GaAs layers

The submillimeter wavelength region is the last undeveloped spectral window in astronomy. The poor transmission of the atmosphere, and the lack of high-performance detectors prevent astronomical observations in this window. We have recently started a development of photoconductors utilizing shallow donor levels in GaAs semiconductors. The GaAs photoconductor promises to be a good candidate of a photo detector for use in future space mission for submillimeter astronomy. We have constructed facilities for liquid-phase epitaxy to obtain ultra-pure GaAs crystals which were absolutely necessary for a fabrication of photoconductors. The first experimental results are reported.