New approach for high-speed, high-sensitivity photodetectors

The bandwidth-efficiency product of ultra high-speed pin photodetectors has been severely limited by the thickness of the absorbing layer, the diode RC time constant, and the parasitic capacitance from the periphery of device. In this paper, we propose and demonstrate a novel long-wavelength detector structure with a mushroom-like mesa and an air-bridged coplanar metal to significantly cut down both the diode RC constant as well as the parasitic capacitance. The quantum efficiency of this structure can be further enhanced to close to 100 % if wafer fusion is used to bond the In/sub 0.53/Ga/sub 0.47/-InP detector to a GaAs/AlAs quarter-wave stack (QWS), followed by deposition of a Si/SiO/sub 2/ QWS to form a Fabry-Perot cavity.