High-speed, efficient metal - semiconductor - metal photodetectors

Design principles and the fabrication technique of highly efficient, high-speed photodetectors based on MSM nanostructures are developed. To efficiently confine light in the region of the strong field as well as to decrease light losses due to reflection from the diode contacts, use is made of a nanoscale interdigital diffraction grating and a multilayer Bragg grating. Measurements of the reflection coefficients and the quantum efficiency for a multilayer structure are in good agreement with theoretical estimates. A record-high quantum efficiency (QE = 46 %) is obtained for high speed MSM photodetectors. The detector has a high spectral selectivity (Δλ_1/2 = 17 nm) at a wavelength of 800 nm. Taking into account the diode capacitance and the drift time of photogenerated carriers, the performance of the detectors under study is ~ 500 GHz. The low level of the dark current density in the structures under study (j = 1 pA μm^-2) makes it possible to realise on their basis highly sensitive, high-speed selective detectors of optical radiation.