We propose and simulate a device structure of resonant cavity-enhanced quantum-dot infrared photodetector (RCE-QDIP). The RCE-QDIP consists of a conventional n-in QDIP sandwiched by a bottom GaAs/Al 2 O 3 distributed Bragg reflector and a top mirror of Ge/SiO 2 sub-wavelength grating. Aiming for detecting mid-infrared at 8 lm, the total thickness of the device is only $7.7 lm. According to our simulation, the external quantum efficiencies of RCE-QDIP could be as high as 59%-78% with the enhancement factors of 7-30, compared with a conventional QDIP. The proposed RCE-QDIP is highly feasible as the various fabrication parameters are considered.

We have proposed and fabricated a new mid-infrared reflector using the guided-mode resonance (GMR). The GMR reflector consists of subwavelength Ge grating on GaAs substrate with a low-refractive-index SiOx layer in between. With a total thickness of about 2 μm, a near-100% reflectivity at 8 μm has been obtained both theoretically and experimentally.