Ultrahigh speed modulation-doped heterostructure field-effect photodetectors

Abstract

We have developed a sensitive, ultrahigh speed photodetector which has a structure of a modulation-doped AlxGa1−xAs/GaAs field-effect transistor. In spite of a large gate-drain spacing of >8 μm and a gate length of >20 μm, this detector exhibited a rise time of 12 ps and a full width at half-maximum of 27 ps. When tested by a 8200-Å GaAs injection laser, the detector showed an ac (>20 MHz) external quantum efficiency of >630%, i.e., 9 times more sensitive than a pin photodiode. In view of its high sensitivity, ultrahigh speed, and compatibility with modulation-doped field-effect transistors, this detector has promise for a variety of high-speed optical applications.