Systematic studies for improving device performance of quantum well infrared stripe photodetectors

Abstract

<jats:title>Abstract</jats:title><jats:p>The integration of quantum well infrared photodetectors with plasmonic cavities has allowed for demonstration of sensitive photodetectors in the mid-infrared up to room-temperature operating conditions. However, clear guidelines for optimizing device structure for these detectors have not been developed. Using simple stripe cavity detectors as a model system, we clarify the fundamental factors that improve photodetector performance. By etching semiconductor material between the stripes, the cavity resonance wavelength was expected to blue-shift, and the electric field was predicted to strongly increase, resulting in higher responsivity than unetched stripe detectors. Contrary to our predictions, etched stripe detectors showed lower responsivities, indicating surface effects at the sidewalls and reduced absorption. Nevertheless, etching led to higher detectivity due to significantly reduced detector dark current. These results suggest that etched structures are the superior photodetector design, and that appropriate sidewall surface treatments could further improve device performance. Finally, through polarization and incidence angle dependence measurements of the stripe detectors, we clarify how the design of previously demonstrated wired patch antennas led to improved device performance. These results are widely applicable for cavity designs over a broad range of wavelengths within the infrared, and can serve as a roadmap for improving next-generation infrared photodetectors.</jats:p>

Near-field resonant photon sorting applied: dual-band metasurface quantum well infrared photodetectors for gas sensing

“…Our dual-band metasurface QWIPs show a maximum unpolarized responsivity of 2.1 A/W at a peak wavelength of 6.9 μm (external quantum efficiency: 38%), comparable to previously demonstrated single-band stripe metasurface QWIPs [21]. Tailoring one resonance to an absorption peak of NO 2 (6.25 μm) and the other to a non-absorbing reference wavelength (7.15 μm), we determine NO 2 gas concentration with 10 ppm accuracy and 1 ms response times, suitable for transient gas sensing applications demanding fast and accurate detection such as combustion engine diagnostics.…”

“…The QWIP layer used in this study consists of a single 4 nm GaAs quantum well layer sandwiched by two 50 nm Al 0.3 Ga 0.7 As barrier layers and two 48 nm GaAs contact layers [21,25,32], a total thickness T = 200 nm, which exhibits a photoconductive responsivity peak at 6.7 μm [21,25]. Stripe cavities consist of a t m1 = 100 nm thick Au stripe and a thick Au substrate (650 nm, but set at t m2 = 200 nm for calculations) sandwiching the QWIP layer.…”

“…Stripes with widths of L 1 and L 2 (L 1 < L 2 ) are alternated with a period P/2 ( Figure 1A). The QWIP layer between the QWIP stripes is removed [21,25] for electrical isolation between neighboring stripes. The resonance wavelengths λ 1 and λ 2 , determined by L 1 and L 2 , respectively, should fall within the absorption range of the quantum well (6.0-7.4 μm).…”

“…Here, we demonstrate a dual-band photodetector for NDIR gas sensing based on resonant photon sorting consisting of two electrically isolated, interdigitated stripe MDM cavities sandwiching quantum well infrared photodetectors (QWIPs), metasurface QWIPs [21][22][23][24][25], with different resonance wavelengths. Metasurface QWIPs are based on intersubband transitions (ISBT) in quantum wells.…”

“…An intense vertical electric field, essential for ISBT absorption [26,27], is provided by the MDM cavity through rotation of the incident horizontal electric field to vertical, and intensity enhancement [14,28,29]. High responsivities [23], fast response times [24,30], and detectivities approaching theoretical limits [21,24,25,31], sufficient to replace toxic HgCdTe presently dominant at wavelengths beyond 5 μm, have been demonstrated.…”