Study On Al(In)GaN Ultraviolet Detector On Silicon Substrate

Sapphire substrates are hard,difficult to thin,and have serious surface warpage.Silicon carbide substrates are small in size and expensive.In contrast,silicon substrates have low price,large wafer size,high crystal quality,good surface flatness and mature technology.Therefore,it has great application value in the field of low-cost,large-area array,and high-uniformity Al(In)GaN ultraviolet detectors.However,the lattice mismatch and thermal mismatch of the silicon substrate and Al(In)GaN are relatively large,and the epitaxial quality is poor.With the advancement of grid selection growth,intermediate layer,buffer layer,superlattice and other technologies,the epitaxial quality,thickness and area of Al(In)GaN on silicon substrate have been continuously improved,and it has been widely used in the field of light-emitting diodes.By changing the Al composition and In composition,the forbidden band width of AlGaN and InGaN varies from 0.76e V to 6.2e V,and the corresponding absorption spectrum ranges from 1632nm to 200nm,covering the entire solar-blind ultraviolet(200-300nm)and near ultraviolet(300-400nm),becoming important ultraviolet detection materials.The MOCVD method was used to grow a GaN/InGaN/GaN p-i-n structure epitaxial layer on silicon(111)substrate,and InGaN ultraviolet detector on silicon substrate was successfully prepared,and PL spectrum,the I-V characteristics and spectral properties of the device were tested.In-depth research on silicon substrate removal technology was carried out.The silicon substrate of the UV detector was removed by wet etching,and the performance of the device before and after removal was tested,which lays the foundation for the application of low-cost,large-area-array,high-uniformity silicon substrate InGaN ultraviolet detectors.The preparation process of the frontal irradiation InGaN UV detection unit device on the silicon substrate is introduced,and the performance of the device is tested.In view of the large lattice mismatch and thermal mismatch of InGaN material on silicon substrate,the large dislocation and defect density,and the large leakage current on the detector surface,the passivation of Ru Cl₃,Na₂S and nitric acid on the device was studied.The research shows that:Compared with the devices without passivatioin,the reverse dark current of the device after the surface passivation by Ru is reduced by 2-3orders of magnitude,and the peak response rate of the device after the mesa passivation by S is increased by 7-12%.The peak response rate of the device at 362nm is 0.154A/W,the external quantum efficiency is 53%,the dark current is 7.2×10^-12A under zero bias,and the response band is 310-380nm.Aiming at the problem of the opacity of the silicon substrate,the mechanical polishing,wet etching,dry etching and other process methods are introduced,and the characteristics of these methods are compared.The substrate of the 640×8 InGaN ultraviolet line array is successfully removed by the chemical wet etching,and the performance of the device before and after the substrate is tested.Experiments have found that wet etching can effectively remove the silicon substrate,and the corrosion rate is very high,but the release of stress at the epitaxial interface will break the epitaxial film and damage the readout circuit after the corrosive liquid penetrates.The Al component was introduced into the AlGaN complex refractive index model,the full range Al component AlGaN complex refractive index model was established,combined with the multilayer optical film model,the transmission spectra of multiple experimental samples were fitted,and a good result was obtained.A fast analysis method for the transmission spectrum of multilayer films is proposed,which provides a theoretical reference for AlGaN device structure optimization,process improvement,and performance improvement.