Multi-Spectral Active IR Sensing
Abstract
This program has developed resonant cavity infrared detectors (RCIDs) with very thin InAsSb/InAs superlattice absorber layers. An exemplary RCID placed an absorber with thickness only 100 nm inside a cavity formed by a GaAs/AlGaAs distributed Bragg reflector bottom mirror and Ge/SiO2/Ge top mirror. At a low bias voltage of 150 mV, the external quantum efficiency (EQE) reached 58% at the resonance wavelength 4.6 microns, with linewidth 19-27 nm. The thermal background current for a realistic system scenario with f/4 optic that views a 300 K scene was estimated by integrating the photocurrent generated by background spanning the entire mid-IR spectral band (3-5 m). The resulting specific detectivity is a factor of 3 lower than for a state-of-the-art broadband HgCdTe device at 300 K, where dark current dominates the noise. However, at 125 K where the suppression of background noise becomes critical, the estimated specific detectivity of D* of 5.5e12 cm Hz/W is more than 3x higher. This occurs despite a non-optimal absorber cut-off that causes the EQE to decrease rapidly with decreasing temperature, e.g., to 33% at 125 K. The RCIDs advantage over the broadband device depends critically on its low EQE at non-resonance wavelengths, which was </= 1% in the range 3.9-5.5 microns. Simulations using NRL MULTIBANDS found that at ambient temperature, the primary source of dark current is impact ionization in the top contact layer. This can be mitigated in future work by reducing the doping concentration in the top contact layer. We expect the planned design modifications to substantially enhance D* at all temperatures from cryogenic to ambient. Another RCID advantage is high frequency response, because photoexcited carriers can be extracted rapidly from the very thin absorber. Collaborator Intraband, LLC performed high-frequency measurements on an RCID grown by NRL and processed by Praevium to have a smaller mesa diameter of 25 microns for low capacitance.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 04, 2024
- Accession Number
- AD1218338
Entities
People
- C. L. Canedy
- Chul Soo Kim
- E. H. Aifer
- Eric M. Jackson
- I. Vurgaftman
- J. M. Auxier
- Jerry R. Meyer
- Jill A. Nolde
- M. R. Pauli
- R. L. Espinola
Organizations
- United States Naval Research Laboratory