New-generation infrared detectors call for higher operation temperature and polarization sensitivity. For traditional HgCdTe infrared detectors, the additional polarization optics and cryogenic cooling are necessary to achieve high-performance infrared polarization detection, while they can complicate this system and limit the integration. Here, a mixed-dimensional HgCdTe/black phosphorous van der Waals heterojunction photodiode is proposed for polarization-sensitive midwave infrared photodetection. Benefiting from van der Waals integration, type III broken-gap band alignment heterojunctions are achieved. Anisotropy optical properties of black phosphorous bring polarization sensitivity from visible light to midwave infrared without external optics. Our devices show an outstanding performance at room temperature without applied bias, with peak blackbody detectivity as high as 7.93 × 10 10 cm Hz 1/2 W −1 and average blackbody detectivity over 2.1 × 10 10 cm Hz 1/2 W −1 in midwave infrared region. This strategy offers a possible practical solution for next-generation infrared detector with high operation temperature, high performance, and multi-information acquisition.

Ferroelectric materials have shown great value in the modern semiconductor industry and are considered important function materials due to their high dielectric constant and tunable spontaneous polarization. A ferroelectric field effect transistor (FeFET) is a field effect transistor (FET) with ferroelectric polarization field introduced to regulate carriers in semiconductors. With the coupling of ferroelectric and semiconductor, FeFETs are attractive for advanced electronic and optoelectronic applications, including emerging memories, artificial neural networks, high-performance photodetectors, and smart sensors. In this review, representative research results of FeFETs are reviewed from the perspective of structures and applications. Here, the background and significance of ferroelectrics and FeFETs are given. Furthermore, methods of building FeFETs in different structures and physical models describing the characteristics of FeFET are introduced. Important applications of FeFETs in electronics and optoelectronics are presented, with a comparison of performance between FeFETs and FETs without ferroelectrics, including memories and memristive devices, photodetectors, negative capacitance FETs, sensors, and multifunctional devices. Finally, based on the above discussions, promising applications and challenges of FeFETs are summarized.

Two-dimensional GaGeTe flakes with different thicknesses from 80 to 2.2 nm (bilayer) were exfoliated and transferred to a SiO2/Si substrate. A series of samples with different thicknesses were prepared and identified by optical microscopy, atomic force microscopy, and Raman spectrum. Raman modes strongly dependent on the layer thickness and characteristic Raman-active modes for few-layer (FL) GaGeTe flakes are demonstrated. These vibration modes of FL GaGeTe show a linear red-shift phenomenon with increasing temperature and their full width at half maximum of the Raman mode exhibits a weak temperature dependence below 200 K, and then, a linear increase with temperature. The electrical conductivity is 96.48 S/cm for 74 nm flakes and drops exponentially to 2.27 × 10−7 S/cm for 7 nm ones because of the bandgap widening with the decrease of layer thickness, which is evidenced by the work function increase from 4.4 to 4.96 eV, when the thickness decreases from 80 to 2.2 nm. Moreover, the electrical conductivity performs two different temperature dependence behaviors on the thickness, indicating a transition from semimetal for bulk to semiconductor for FL GaGeTe, which agrees well with that of the theoretical calculation.