Yagi-Uda nanoantenna enhanced metal-semiconductor-metal photodetector

An array of 400 nanolithographic Yagi-Uda antennas on a metal-semiconductor-metal rectifier photodetector demonstrates control of wavelength selectivity and directivity. The nanoantenna array response is obtained using a direct electrical measurement approach. Resonances in rectified photocurrent are detected at the incident electromagnetic radiation of free-space wavelengths 1110 nm and 1690 nm, corresponding to scaled effective wavelengths of 388 nm and 776 nm, respectively. The scaling is consistent with a theory based on plasmonic effects in nanoscale devices at optical frequencies, and the two resonant wavelength modes are found to match at, respectively, full-wavelength and half-wavelength operation of the detector dipole element. Quantum efficiencies are estimated as 5.1% and 3.1% at 1110 nm and 1690 nm wavelengths, respectively, representing a fourfold increase over a device lacking the antenna array.