Preparation Of Gase-based Two-dimensional Semiconductor Heterojunction And Its Photoelectric Properties

In recent years,reports based on nanometer-thickness two-dimensional material photodetectors have emerged.Two kinds of two-dimensional materials with different energy bands can be stacked like a Lego brick to form a heterojunction,which is beneficial to expand the detection range of the photodetector.In view of the excellent photoelectric characteristics and existing defects exhibited by GaSe,we have systematically studied GaSe-based heterojunction photodetectors.We explored the mechanical stripping preparation method of two-dimensional material and successfully peeled off the thin two-dimensional GaSe and MoS₂ sheets.A two-dimensional material transfer system was built to achieve transfer and in-situ stacking of two-dimensional material.In order to study the intrinsic light absorption characteristics of GaSe materials,a metal-semiconductor-metal?MSM?photodetector based on GaSe was first fabricated.Under illumination,GaSe-based MSM photodetector exhibit strong light absorption characteristics.GaSe-based MSM photodetector demonstrates a time response of²0 ms.On this basis,a GaSe/MoS₂ heterojunction photodetector with Ni/Au electrode was fabricated.Due to the existence of the photovoltaic effect,the device is self-driving.Under illumination,the photocurrent increases linearly with the increase of incident light power.The responsivity,external quantum efficiency,and specific detectivity of the GaSe/MoS₂ heterojunction photodetector with Ni/Au electrode are up to 111 mA/W,31%,and 5.7×10¹⁰ cmHz^1/2/W,respectively.The time response of the GaSe/MoS₂heterojunction photodetector with Ni/Au electrode is⁶20?s,which is 32 times faster than GaSe-based MSM photodetectors.However,the photoresponse of the GaSe/MoS₂heterojunction photodetectors with Ni/Au electrode is very weak in the near-infrared spectra.Through theoretical analysis,we found that the Schottky-contact between the electrode and GaSe/MoS₂ has an adverse effect on the photodetection performance of the GaSe/MoS₂ heterojunction.Through further experimental research,we found that the Schottky-contact between various metal electrodes and GaSe/MoS₂ is inevitable.Therefore,we explored ITO electrodes that form Ohmic-contacts with both GaSe and MoS₂.Thanks to the Ohmic-contact between ITO and GaSe/MoS₂,the responsivity,external quantum efficiency,and specific detectivity of the GaSe/MoS₂ heterojunction photodetectors with ITO electrodes are up to 670 mA/W,160%,and 2.3×10¹¹ cmHz^1/2/W,respectively.The time response of the GaSe/MoS₂ heterojunction photodetectors with ITO electrodes is¹55?s,which is 4 times than the GaSe/MoS₂ heterojunction photodetector with Ni/Au electrode and about 300 times faster than the previous reports.Compared to the GaSe/MoS₂ heterojunction photodetectors with Ni/Au electrodes,the GaSe/MoS₂ heterojunction photodetectors with ITO electrodes have more excellent photoelectric detection performance:responsivity,external quantum efficiency and specific detectivity at 808 nm near-infrared increased by 90 times,100 times and 60 times,respectively.The above research results indicate that the Ohmic-contact of the electrode plays a key role in improving the photoelectric performance of the GaSe/MoS₂heterojunction photodetector,which provides new ideas for the research of the two-dimensional material photodetector.In addition,two-dimensional material photodetectors based on ITO electrodes are expected to be integrated on transparent substrates such as glass and have broad application prospects.