Infrared dual-band photodetector is an important multi-spectral detector, especially in the near infrared/short-wave infrared region, which has stronger penetration ability than visible light, and can identify cold background objects with lower loss than mid-wave infrared, so it is widely used in civil and military fields. At present, infrared dual-band detectors are mainly faced with the challenges of untunable spectrum, complex device structure and difficult to combine with readout integrated circuits.
Recently, the research team developed a spectrally tunable near-infrared/short-wave infrared dual-band detector, Related research results are presented as "Bias-Selectable Si Nanowires/PbS Nanocrystalline Film n -- n Heterojunction for NIR/SWIR Dual-Band. Photodetection, published in Advanced Functional Materials (2023: 2214996.). The first author is Xu Chenhao, the corresponding author is Professor Luo Linbao, mainly engaged in the research work of new high-performance semiconductor optoelectronic devices and related optoelectronic integration technologies.
In this study, a silicon nanowire/lead sulfide heterojunction photodetector was prepared by a solution method (as shown in Figure 1(a)). The process is simple and the spectral response of the silicon-based detector is successfully broadened to 2000 nm. COMSOL software analysis based on finite element analysis shows that, on the one hand, the ordered silicon nanowire array has a larger device area, which improves the carrier transport ability, and the nanowire array has better periodicity, and the incident Light can be continuously reflected between the nanowire structures, producing a typical light-trapping effect. On the other hand, small-sized nanowire arrays can be regarded as micro-resonators, which can form HE₁ₘ resonant modes to enhance the light absorption of specific incident light.
By modulating the polarity of the applied bias voltage, the device can switch between three detection modes: near-infrared/short-wave infrared dual-band detection, near-infrared single-band detection, and short-wave infrared single-band detection. The device also has high sensitivity, with a detectivity as high as 2.4 × 10¹⁰ Jones at 2000 nm illumination, which is higher than most short-wave infrared detectors.
FIG. 1 Dual-band infrared detector structure and related simulation and experimental results
Fig. 2 Near-infrared/short-wave infrared dual-band detection with adjustable bias voltage and the change curve of detection rate with light intensity
In addition, the study also built a single-pixel photoelectric imaging system (as shown in Figure 3 (a)). Under 2000 nm light, when bias voltages of -0.15 V and 0.15 V are applied, the device can image a simple English letter . However, when no bias voltage is applied, the image cannot be clearly imaged. This shows that when only a small bias voltage needs to be applied to the device, the working area of the imaging system can be adjusted from near-infrared to short-wave infrared, which has high flexibility.
Figure 3 Photoelectric imaging system and imaging results
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