A superlattice-based resonant cavity-enhanced photodetector operating in the long-wavelength infrared

Abstract

The design, fabrication, and characterization of a resonant cavity-enhanced photodetector (RCE PD) operating in the long-wavelength infrared regime are demonstrated. The incorporation of the low bandgap InAs/InAs0.70Sb0.30 type-II strained-layer superlattice into the absorber layer of the detector cavity, along with the high-reflectivity (Rm > 0.9) AlAs0.08Sb0.92/GaSb distributed Bragg reflector pairs, results in resonant enhancement at 7.7–7.8 μm, which is a spectral region relevant in applications in sensing of chemical warfare agents and in medical biomarker diagnostics. These resonant wavelength peaks also display a high quality factor in the range of 76–86 and a small temperature coefficient of 0.52 nm K−1. An nBn architecture, where an Al0.71Ga0.29As0.08Sb0.92 layer acts as a barrier for majority electrons while minimizing the valence band offset with the absorber, is also incorporated into the cavity in order to improve the electrical properties of the detector. Spectral response measurements yield a peak external quantum efficiency of 14.6% and a peak responsivity of 0.91 A W−1 at 77 K and −0.8 V; meanwhile, a dark current density of 2.0 × 10−4 A cm−2 at 77 K results in a specific detectivity of 3.7 × 1010 cm Hz1/2 W−1, coming close to the theoretical background-limited D* of an ideal broadband photovoltaic detector with the superlattice composition as that of the RCE PD.

Solid-state micro-spectrometer based on a linear array of infrared resonant-cavity-enhanced photodetectors

“…We have already demonstrated RCE-PDs between 2.2 µm -7.8 µm using a range of III-Sb absorbers and T2SLs. [1][2][3][4][5] In theory, III-Sb RCE-PDs could be created operating between 1.5 and ~12 µm using GaSb, InGaAsSb, InAsSb and InAsSb-InAs T2SLs. This spectral range covers the SWIR, MWIR and LWIR containing absorption fingerprints in Figure 6.…”

Plasmon-enhanced distributed Bragg reflectors

“…Without a significant increase in the refractive index contrast of the DBR constituent materials, total DBR thickness quickly becomes impractical for real world device applications. Despite the mirror thickness requirements, MWIR resonant cavity photonic devices, including vertical-cavity surface-emitting lasers (VCSELs) [1]- [4], resonant-cavity light-emitting diodes (LEDs) [5], [6] and photodectors [7]- [9] have all been demonstrated using AlAsSb/GaSb DBR structures, with a refractive index contrast ∆n ≈ 0.6. With these materials, a 20-pair DBR designed for 4 µm operation requires nearly 12 µm of epitaxial growth and this increased thickness greatly increases fabrication complexity and concomitantly decreases tolerances and yield.…”

Resonant Cavity–Enhanced Photodiodes for Spectroscopy of CH Bonds

“…III−V‐based RCE–PDs have previously been demonstrated at multiple wavelengths, from the shortwave infrared at , [ 7 ] up to . [ 8 ] However, the MWIR has seen the most effort. [ 9–12 ] RCE–PDs grown on GaSb substrates have become well established, whereas for the target of , a lattice‐mismatched RCE–PD was grown on a GaAs substrate by Green et al [ 13 ] RCE–PDs on InAs substrates have also been touched upon by O’Loughlin et al [ 11 ]…”