Design Consideration and Demonstration of Resonant-Cavity-Enhanced Quantum Dot Infrared Photodetectors in Mid-Infrared Wavelength Regime (3–5 $\mu{\rm m}$)

Lattice-mismatched-strain-driven, defect-free, 3-D islands, dubbed self-assembled quantum dots (SAQDs), currently provide the most advanced platform for quantum-dot-based devices with successful applications to SAQD lasers and considerable potential for infrared detectors. For the latter, one of the limitations is the short optical path length owing to the difficulties in creation of large numbers of quantum dot layers without formation of structural defects arising from accumulated strain. This limitation can be considerably overcome by creation of an appropriate resonant cavity to enhance the optical field in the SAQD regions. In this paper, we demonstrate resonant-cavity-enhanced quantum dot infrared photodetectors in the mid-infrared (MIR, 3-5 μm ) regime. For effective enhancement, the SAQDs are designed to generate a very narrow peak (Δλ/λ ~ 10%) in the intraband photocurrent response in the MIR range utilizing short period superlattices as the quantum confining layers. Incorporating such SAQD layers at specific enhanced electric field regions within the resonant cavity comprising a two-pair GaAs/air-gap back mirror and a GaAs surface front mirror, we have obtained QDIP detectivity enhancement of ~ 8-12 times.