Preparation And Photo-detecting Performances Of GeSe-based Micro-crystals

The development of photodetectors has a history of decades.They are very important part of modern optoelectronic subsystems.In the process of converting optical signals into electrical signals,it is used to receive signals from external light,which is equivalent to human eyes.Among photodetector devices,the choice of optoelectronic semiconductor material is very important,it directly determines the performance of the photodetector.Many photodetector devices,such as Ge-based,Si-based,HgCdTe-based,InGaSe-based photodetector devices,have been used extensively.Nowadays,with the advancement of science and technology and the development of society,people have higher and higher requirements for the performance of photodetector materials and their devices.The trend of devices is more integrated,efficient,sensitive and broad spectrum.Therefore,low-dimensional（0D,1D,2D）optoelectronic materials have entered everyone’s field of vision.ZnO nanowires,graphene,black phosphorus,and transition metal sulfur compounds（TMDs）are particularly one-or two-dimensional optoelectronic materials that have been studied in the last decade.But they all have their own deficiencies and limitations.For example,graphene’s zero band gap has limited its application in the field of photodetection.The instability of black phosphorus in the air also limits his practical application and so on.GeSe as an IV-VI compound semiconductor has a layered structure similar to black phosphorus and has anisotropic electron transport properties.High photoelectric response,fast photoelectric response time,adjustable band gap,non-toxic,environmentally friendly,common elements,stable presence in air is the advantage of GeSe as a photodetector material,which also determines GeSe in the future Photodetector applications have great potential.However,there are few studies on GeSe,especially the preparation of micro-nanometer single crystal materials,high photoelectric responsivity,sensitive photoelectric response time,and performance of photodetectors in the near infrared range.This paper mainly carried out the following research works:（1）GeSe micro-belts and micro-sheets were prepared by the"one-pot method".In this method,GeI₄ is used as the source of Ge,SeO₂ is used as the source of Se,and the GeSe micro-belts and micro-sheets were synthesized by heating in a solvent at 320℃for 6 hours.When the octadecene was used as a solvent,the GeSe micro-sheets were synthesized,and when the oleic acid was used as a solvent,the GeSe micro-belts were synthesized.According to TEM and HRTEM images,the micro-belts were grown along the[010]direction.To explore the formation mechanism of GeSe microcrystals,we mixed the solvents at different concentrations（oleic acid/octadecene ratios are:0:100;20:80;40:60;60:40;80:20;100:0）,the obtained GeSe crystals gradually change from micro-sheets to micro bands with increasing oleic acid concentration,and FTIR results show that oleic acid adsorption inhibits growth in the[001]direction.The GeSe micro-sheets and micro-belts were subsequently made into photodetector devices.Both devices showed very good photoelectric response,and the micro-belt photodetector shows higher responsivity,detectivity and faster response time.The responsivity of the micro-sheet photodetector under 532 nm light is up to 5562 A/W,and the detection rate is 3.01×10¹² Jones.These good performances reflect the considerable application prospects of GeSe micro-sheets and micro-belts in photodetectors.（2）By doping cations in the GeSe,the band gap of GeSe is adjusted and the photoelectric detection performance is improved.The Ge_1-xSn_x Se micro-crystals were synthesized by doping Sn ions in the synthesis of GeSe micro-crystals,which showed a hexagonal sheet-like structure.The band gap of Ge_1-xSn_x Se decreased with the increase of doping concentration of Sn ions.When x=0.2,the band gap of Ge_1-xSn_xSe drops to0.914 eV,which is about 0.1 eV lower than the band gap of GeSe.The structure is more suitable for the near infrared band.The more holes were generated when the Ge ions were replaced by Sn ions.As the increase of doping concentration,the resistivity gradually decreased,and the carrier concentration gradually increased.Subsequently,the Ge_0.8Sn_0.2Se micro-crystal was prepared as a photodetector device,and its photocurrent was greatly improved compared with the original GeSe device.The responsivity of the photodetector under 532 nm light increased from 824 A/W to 5759A/W.The responsivity at 980 nm increased from 180 A/W to 3042 A/W.,the responsivity at 1319 nm increased from 14 A/W increased to 143 A/W.The Ge_1-xSn_xSemicro-crystals provide a new idea for the enhancement of GeSe performance and the adjustment of energy bands.The photoelectric performance gain reflects the good application value of the Ge_1-xSn_xSe photoelectric materials and their detectors in the visible-near infrared.