In recent years, medium-wave infrared has gained more and more important applications in thermal imaging, molecular identification, free space communication and optical radar. The currently used more HgCdTe infrared detectors need low temperature refrigeration, the use of very inconvenient, the price is extremely expensive; uncooled (room temperature) infrared detector can meet a wide range of applications, as infrared detection research in the field of great concern Degree of direction.
At present, the mainstream technology of uncooled infrared detectors is a thermistor microbolometer, which is divided into two kinds of vanadium oxide detectors and amorphous silicon detectors according to different thermistor materials used, but the detection rate is lower than that in the response Time is slow, and its core technology is also blocked by foreign countries.
In response to this technical challenge, Prof. Miao Feng's team and research team from Nanjing University School of Physics successfully achieved room temperature performance with new narrow bandgap two-dimensional material "arsenic" (b-AsP) and related van der Waal's heterojunction The current commercial technology highly sensitive mid-wave infrared photoelectric detection, to promote the application of two-dimensional materials in the field of infrared detection has taken an important step. This work was recently published in Science Advances [3, e1700589 (2017)].
Fig. 1 (A) Response signal of mid-wave infrared of arsenic phosphorus field effect device 8.05 μm at room temperature, inset: Photovoltaic response (top) and structure schematic of device (bottom); (B) (C) Photomicroscopy of b-AsP-MoS2 heterojunction photodetector, with a scale of 5 μm; (D) Room temperature b -AsP-MoS2 heterojunction photodetector ratio detection ratio compared with commercial PbSe detectors and commercial thermistor detectors.
In recent years, the group has made some progress in the field of two-dimensional material visible and near-infrared photodetectors (Nano Lett. 16, 2254 (2016); Adv. Func. Mater. 26, 1938 (2016). On this basis, this work selected a new type of narrow-bandgap materials such as arsenic and phosphorus. This type of material is obtained by doping the same group of elemental arsenic with black phosphorus. A specific proportion of the black arsenic phosphorous b-As0.83P0.17 has been found to have a band gap that can be adjusted to ~ 0.15 eV, demonstrating potential for use in mid-infrared detection .
In this work, firstly, a thin layer sample of b-As0.83P0.17 was obtained by mechanical cleavage. A field effect phototransistor was prepared. The response of 8.05 μm mid-wave infrared was observed at room temperature (FIG. 1A) A window of atmosphere. By further systematic study on the working mechanism of the detector, it was found that the photovoltaic effect and the photothermal effect are respectively dominant at different back-gate voltages (Fig. 1B).
In order to overcome the challenge of narrow bandgap semiconductor with dark current and noises at room temperature, which leads to the significant decrease of the device performance, the different doped n-type MoS2 and b-As0.83P0.17 (p-type ) Are stacked together to form a Van der Waals heterojunction (FIG. 1C). The test results show that the structure heterojunction effectively reduces the dark current and noise of the device, and the detection ratio at room temperature can reach as high as 5 × 109 Jones, which is one point higher than the peak detection rate of the widely used PbSe infrared detector Magnitude (Figure 1D). The results also demonstrate the great potential of van der Waals heterojunctions based on narrow-band two-dimensional materials in the area of medium-wave infrared detection.
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