Properties of LT MBE GaAs for photomixing up to THz frequencies

Abstract

The properties of low-temperature-grown MBE GaAs layers, as-grown and annealed (T/sub g/=200-420/spl deg/C, T/sub a/=600/spl deg/C), are evaluated in relation to the performance of a photomixer. In all annealed layers the photocarrier life time /spl tau//sub e-h/= 0.20-0.25 ps is found. Microwave capacitance of MSM structures is measured and RC-limited bandwidth of 460 GHz follows from /spl tau//sub e-h/ and /spl tau//sub RC/ evaluation. The carrier mobility in as-grown and annealed layers increases from /spl mu//sub H//spl les/1 cm/sup 2//V s to SI GaAs bulk values with increase in the growth temperature. The breakdown field in annealed layers is /spl cong/280 kV/cm if grown at 200-250/spl deg/C and decreases to /spl cong/40 kV/cm if T/sub g/ increases to 420/spl deg/C. Thus, photomixer conversion efficiency /spl epsiv//sub r/ can be optimized.