High-performance Long-wave Infrared Photodetectors Based on Alloyed Two-dimensional Materials

Description

Infrared photodetectors that can detect infrared light in wavelength range of 1-14 μm have been extensively studied since they are the key components in various important applications like surveillance and rescue, optical communications, remote sensing and biomedical imaging modalities. Layered two-dimensional (2D) materials have been recently demonstrated to be promising absorbers for high-performance infrared photodetectors. The key advantage of layered2D materials is the absence of surface dangling bonds since layers stack together through van derWaals interaction. Such unique advantage allows the use of thin 2D semiconductors (down to monolayers) as absorbers in infrared photodetectors to reduce noise without detrimental effects and construction of p-n heterojunctions without considering the lattice matching. However, the lack of 2D semiconductors with suitable bandgaps and extremely low absorption in thin 2D layers have become two major bottlenecks for fabrication of high-performance 2D material-based infrared photodetectors, especially for long-wave infrared (LWIR) band (8-14 μm). This project aims to tackle the two bottlenecks by design/synthesis of novel narrow-bandgap alloyed 2D semiconductors and nanooptics design/integration, respectively. The PI has rich experience on growth/exfoliation and characterization of layered bulk crystals, design/fabrication of nanooptics and device fabrication/test of infrared photodetectors. We will synthesize two alloyed 2D semiconductors, including PtxPd1-xSe2 and PtS2xSe2(1-x), to obtain 2D materials with suitable bandgaps (~100-150 meV), which will be used as absorbers for fabrication of LWIR photodetectors. Our preliminary results have demonstrated that the photoconductor based on mechanically exfoliated Pt0.86Pd0.14Se2 alloyed thin nanoflake can detect LWIR light up 12 μm Nanooptics, including optical cavity substrates and optical nanoantennas, will be designed to significantly enhance the absorption in thin 2D semiconductors and/or maximize the light intensity per unit area shining on the active area of detectors, solving the low absorption issue in 2D semiconductors. LWIR photodetectors will be fabricated based on 2D p-n heterojunctions (e.g., PtxPd1-xSe2/Te and PtS2xSe2(1-x)/Te) and integrated with nanooptics to realize high device performance at room temperature. The successful accomplishment of this project will deliver LWIR photodetectors with figure of merits that are comparable with or even superior to that of commercially available infrared photodetectors based on traditional Hg1-xCdxTe semiconductors. Specifically, the fabricated LWIR photodetectors are expected to achieve a room-temperature specific detectivity of >1010 cm Hz1/2 W-1, external quantum efficiency >35%, 3 dB point >100 kHz and response (rise and fall) time on the order of microseconds. Once completed, this project will drive the future development of 2D material-based optoelectronic devices.