High-speed operation of GaN/AlGaN quantum cascade detectors at λ≈1.55 μm

We demonstrate room-temperature, high-speed operation of GaN/AlGaN quantum cascade detectors. The devices are processed as square mesas with 50 Ω coplanar access lines. Frequency response measurements were performed under illumination by a modulated laser diode emitting at λ=1.55 μm. The electrical response exhibits a first-order filter frequency response. For 17×17 μm2 (25×25 μm2) detectors the −3 dB cutoff frequency is 11.4 GHz (6.5 GHz). S-parameter analysis confirms that the cutoff frequency is extrinsically limited and that the speed of the device can be further increased by reducing the device size.