Ultrafast quantum-well photodetectors operating at 10µm with flat frequency response up to 70GHz at room temperature

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Hakl, M | Lin, Q, | Lepilliet, Sylvie | Billet, M | Lampin, Jean-Francois | Pirotta, S | Colombelli, R | Wan, W, | Cao, J, | Li, H | Peytavit, Emilien | Barbieri, S

Edité par HAL CCSD ; American Chemical Society,

publié dans ACS photonics 10.1021/acsphotonics.0c01299. International audience. III-V semiconductor mid-infrared photodetectors based on intersubband transitions hold a great potential for ultra-high-speed operation up to several hundreds of GHz. In this work we exploit a ~350nm-thick GaAs/Al0.2Ga0.8As multi-quantum-well heterostructure to demonstrate heterodyne detection at l~10µm with a nearly flat frequency response up to 70GHz at room temperature, solely limited by the measurement system bandwidth. This is the broadest RFbandwidth reported to date for a quantum-well mid-infrared photodetector. Responsivities of 0.15A/W and 1.5A/W are obtained at 300K and 77K respectively. To allow ultrafast operation and illumination at normal incidence, the detector consists of a 50W coplanar waveguide, monolithically integrated with a 2D-array of sub-wavelength patch antennas, electrically interconnected by suspended wires. With this device architecture we obtain a parasitic capacitance of ~30fF, corresponding to the static capacitance of the antennas, yielding a RClimited 3dB cutoff frequency >150GHz at 300K, extracted with a small-signal equivalent circuit model. Using this model, we quantitively reproduce the detector frequency response and find intrinsic roll-off time constants as low as 1ps at room temperature.

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