POLARIZATION DEPENDENCE OF THE RESPONSE OF MICROMETER AND SUBMICROMETER INGAAS METAL-SEMICONDUCTOR-METAL PHOTODETECTORS

The external quantum efficiency of interdigitated InGaAs metal-semicon ductor-metal (MSM) photodetectors with micrometer and submicrometer el ectrode feature sizes are investigated under front illumination with 1 .3-mu m light polarized perpendicular (TM) and parallel (TE) to the di rection of the finger electrodes, As a result of the lamellar grating structure of the electrode pattern, the external quantum efficiency is observed to be considerably larger for TM polarization when the magni tude of the electrode period is reduced to that of the optical wavelen gth of the incident light. For devices with electrode spacing and widt h as small as 0.3 mu m, the efficiency for TM polarized light exceeds that for TE excitation by about a factor of 6, The temporal waveform o f the response to picosecond optical pulses is found to be independent of the state of polarization and its amplitude scales with the contin uous-wave (CW) quantum efficiency. For applications of MSM photodetect ors, which require high-speed and polarization-insensitive operation, alternative electrode patterns based on circularly shaped finger elect rodes are proposed and analyzed with respect to their electrical circu it properties.