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

Abstract

Resonant cavity‐enhanced photodiodes targeted within the spectral region of absorption by CH bonds are demonstrated. The 3.0 – 3.3 μ m region of the infrared spectrum contains many substances that are useful to measure spectroscopically. However, the measurement of individual substances requires a high spectral specificity, that is achieved by the resonant cavity photodiodes with spectral response widths of < 40 nm . Two material systems are investigated for detection at this wavelength range—an InAs absorber on an InAs substrate and an InAsSb absorber lattice‐matched to a GaSb substrate. The resonance wavelength of the InAs‐based device responds at ≈ 3.3 μ m , closely tuned to an absorption peak of methane to allow precise sensing of this gas. At 300 K a quantum efficiency of 52 % is achieved, with a specific detectivity of 2.5 × 10 10 cm Hz / W . The InAsSb‐based device is sensitive at ≈ 3.7 μ m , but the structure could be tuned to the methane absorption peak. Devices could be simply created to target other substances in the C−H absorption region by altering the layer thicknesses in the structure. Both structures can be used for spectrally specific gas sensing in this region of the infrared.

High-sensitivity mid-wave resonant cavity infrared detectors

“…Promising applications of the MWIR RCIDs include free space optical communication [17,19], chemical sensing [13,23], and on-chip spectroscopy [24].…”

“…U. Lancaster also reported an RCID with InAs-InAsSb superlattice absorber that operated with λ res ≈ 4.4 µm, δλ = 50 nm, 80% EQE, and D* = 2.5 × 10 10 cm Hz ½ /W at 240 K (Γ D* ≈ 0.2) [12]. In 2021, the same group reported a device with bulk InAsSb absorber, λ res ≈ 3.7 µm, and δλ ≈ 40 nm that attained Γ D* ≈ 0.4-0.5 at temperatures from 200 to 300 K [13].…”

Resonant cavity infrared detectors for scalable gas sensing

“…Although not yet available for this study, a new generation of RCIDs is currently being developed at other wavelengths. 13,20,21 To monitor ppm-levels of gases, the gas-absorption signal-to-noise ratio needs to increase while the scalability of the sensor is maintained. Potential ideas include a substrate-matched GaSb meta lens 22 or a reflective cavity.…”

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.…”