Highly Anisotropic GeSe Nanosheets for Phototransistors with Ultrahigh Photoresponsivity

Abstract

Abstract2D GeSe possesses black phosphorous‐analog‐layered structure and shows excellent environmental stability, as well as highly anisotropic in‐plane properties. Additionally, its high absorption efficiency in the visible range and high charge carrier mobility render it promising for applications in optoelectronics. However, most reported GeSe‐based photodetectors show frustrating performance especially in photoresponsivity. Herein, a 2D GeSe‐based phototransistor with an ultrahigh photoresponsivity is demonstrated. Its optimized photoresponsivity can be up to ≈1.6 × 105 A W−1. This high responsivity can be attributed to the highly efficient light absorption and the enhanced photoconductive gain due to the existence of trap states. The exfoliated GeSe nanosheet is confirmed to be along the [001] (armchair direction) and [010] (zigzag direction) using transmission electron microscopy and anisotropic Raman characterizations. The angle‐dependent electric and photoresponsive performance is systematically explored. Notably, the GeSe‐based phototransistor shows strong polarization‐dependent photoresponse with a peak/valley ratio of 1.3. Furthermore, the charge carrier mobility along the armchair direction is measured to be 1.85 times larger than that along the zigzag direction.

Emerging in‐plane anisotropic two‐dimensional materials

“…Moreover, Guo et al reported a polarization-sensitive medium wavelength infrared BP phototransistor, which can operate at wavelength of 3.39 μm and at low power in picowatts range. 76 Figure 6F shows the typical schematic of the polarization-sensitive photodetector of GeAs 2 , 59 similar polarization-sensitive photodetectors have also been fabricated on ReS 2 74 GeSe, 139 ReSe 2 75 and ReS 2 Se 2 (1-x) . 140 Recently, our group reported the polarization-sensitive photodetector based on highly anisotropic 2D GeAs 2 with a dichroic ratio up to 2, 59 and we found that polarization-dependent photocurrent stem from GeAs 2 itself, since both the polarization-dependent photoreponse and reflectance contrast display similar polarizationdependent behavior.…”

Synthesis and photoluminescence of high density GeSe triangular nanoplate arrays on Si substrates

“…[18][19][20][21] Among IV-VI compound semiconductors, GeSe possesses a narrow band gap overlapping well with the solar spectrum, high carrier mobility, low toxicity and air stability, showing great potentials in fabrication of electronic and optoelectronic devices. 18,[21][22][23][24][25] Different GeSe structures including nanoparticles, 26 nanosheets (hexagonal, comb and irregular structures) 3,12,14,18 and thin films 19,25 were fabricated by various methods such as chemical vapor deposition and mechanical exfoliation.…”

Visible‐NIR Photodetectors Based on Low‐Dimensional GeSe Micro‐Crystals: Designed Morphology and Improved Photoresponsivity

“…[20] Some research was also focused on 2D GeSe-based phototransistors, which exhibited ultrahigh responsivity up to or 1.6 × 10 5 A/W, but with long response and decay time (0.28 s and 0.51 s). [21] This is because gate voltage of the phototransistor was favorite to a high responsivity, but the concentration of defects and impurities were still not low enough to get a fast photoresponse. Some micro-size 1D GeSe belts or tubes and 2D GeSe sheets have been synthesized by different solution synthesis methods.…”