Research On Controllable Growth Of One-dimensional GaN Nanomaterial And Its Photodetectors

In recent years,Group III nitrides represented by gallium nitride(GaN)have become the material of choice for preparing ultraviolet(UV)detectors.At present,the research of GaN-based semiconductor materials has also turned to the nanometerization of materials and devices.Because nano-materials have novel characteristics different from bulk materials,they will play a very important role in the construction of nano-optoelectronic devices.However,GaN nanomaterials are difficult to control and prepare,the effective unit output is low,and the performance of the device needs to be improved,which restricts the development of GaN-based UV detectors.Based on this,this thesis has carried out research work on the two major problems of GaN nanomaterial-based photodetectors in the controlled growth of materials and carrier regulation,and successfully prepared high-performance UV photodetectors.The main research contents are as follows.Using the metal catalyst assisted growth method,high-quality one-dimensional(1D)GaN nanowires(Nanowires,NWs)growth was achieved.The effects of growth temperature,NH₃flow rate and plasma RF power on GaN nanomaterials were studied.Temperature is positively correlated with the lateral growth rate of GaN NWs,and novel structures such as pine trees and flakes have been discovered under high temperature conditions.NH₃ content and radio frequency power significantly affect the size and morphology of GaN NWs,and it is easy to induce secondary growth on the surface of GaN NWs.By regulating the induction of plasma,a new type of three-dimensional(3D)structure GaN NWs was synthesized,which has good single crystal characteristics and strong near-band edge emission of 366.8 nm.Constructed a metal-semiconductor-metal(MSM)UV photodetector based on 1D GaN and3D GaN NWs.Based on this,a photodetector based on single 1D GaN and 3D GaN NWs was innovatively prepared.Under UV light irradiation,photo-generated carriers mainly migrate in one-dimensional channels without internal defects and grain boundary scattering.Therefore,carriers can be quickly collected by the electrodes on both sides,and the device exhibits more excellent light sensitivity and response speed..Under 4 V bias,the light responsivity reached2.3×10⁶ A/W and 2.8×10⁶ A/W,and the response rise time(t_r)/decay time(t_d)were 80/100 ms and 180/160 ms,respectively.A new heterostructure of single GaN NWs/intrinsic and two-dimensional(2D)p-type doped molybdenum disulfide(Mo S₂)was designed to realize the preparation of ultra-fast response ultraviolet photodetectors.This type of 1D/2D hybrid integrated device not only has the unique properties of both 1D and 2D materials,but the existence of a built-in electric field can accelerate the separation of photogenerated carriers and improve the response speed of the device.Meanwhile,the efficiency of photo-generated carrier injection after Nb doping is improved.The heterojunction detector based on GaN NWs and p-Mo S₂ exhibits better photoelectric performance.Under 365 nm UV light and 4 V bias,the responsivity reached 2.34×10³ A/W,and the response speed(t_r/t_d)reached 12/20 ms,respectively.