Fabrication And Properties Of InGaN Ultraviolet Detector

In recent years, the applications of the ocean detection such as oil spill are inurgent need of a UV detector which probes>365nm wavelength. But this is beyondthe wavelength range of AlGaN UV detector. Therefore, searching for new Ⅲ-Ⅴcompound material is imminent. The bandwidth of InGaN is in the range of0.7eV(InN) to3.4eV (GaN). Its corresponding wavelength can vary from the ultravioletpart (365nm) to the near-infrared part (1770nm), almost covering the entire solarspectrum. To dectect different light wavelengths, we can adjust the bandwidth ofInxGa1-xN by changing In component. Besides, the InGaN material has manycharacteristics such as high absorption coefficient, high mechanical strength, goodthermal conductivity, strong ability to resist radiation and so on. TheGaN/In0.09Ga0.91N epitaxial layer is grown on sapphire substrate (0001) with themethod of MOCVD. By optimizing individual process such as the etching,passivation, annealing, various ultraviolet detectors were successfully fabricated.The research tested and analysed the electrical and optical properties of the devices,having important guiding significance for the study of the UV focal plane detector.The theories of metal-semiconductor contact, the transmission line model ofthin film materials, heterojunction two-dimensional electron gas are introduced toaim at the p electrode ohmic contact. The researches and analyses of P type materialohmic contact were from three aspects of annealing process, surface treatment, theelectrode structure. Experiments showed that the zero bias resistance was lowestwhen the sample was annealed at550degrees Celsius for5minutes due to theexistence of i-InGaN. After dealing with KOH solution, ohmic contact performanceof the sample was greatly improved. The p-package electrode can be effectivelyimproved the contact characteristics, and performance of materials was highlyaffected by the annealing conditions.According to the requirement of InGaN ultraviolet detector, the cause ofgenerating leakage current was studied and related etching process was optimized.The research was done mainly from the different etching power, different passivationmaterials, wet chemical etching process. The results were analyzed with the data of I-V characteristic curve and the response spectrum. Research showed that the deviceside damage became smaller when the etching power of ICP dry etching was greater.KOH solution wet processing and growth of silicon dioxide passivation layer can reduce the surface leakage current.The fabrication and characterization of InGaN p-i-n ultraviolet photodetectorwere reported in this work. InGaN multilayers were grown in metal-organicchemical vapor deposition (MOCVD). Material etching, passivation, metal contactand other techniques were used in the manufacture of unit front-illuminated InGaNdetector. The current-voltage (I-V) curve showed that current at zero bias was3.70×10-13A and the resistance was4.53×1010Ω. A flat band spectral response wasachieved in the360nm～390nm. The detector displayed an unbiased response of0.22A/W at378nm, corresponding to an internal quantum efficiency of88%. R0Avalues up to1.3×108Ω·cm2was obtained corresponding to D*=1.97×1013cm·Hz1/2·W-1. The photolithography masks of long linear device were designed.InGaN800×8UV long linear focal plane detector was completed successfully with aset of process flow.The design of the InGaN schottky device structure was done and a thin layer oftransparent electrode was grown on i layer InGaN. Through the continuousimprovement of process flow, we got InGaN schottky diodes successfully and testedI-V and C-V characteristics of the device. Based on schottky devices I-V curvefitting, the effective barrier height of InGaN schottky device was0.63eV and idealfactor was3.4both of which were calculated. Comparing with the C-V curves ofschottky devices under the conditions of light and no light, we analysed the reasonsof the induction effect and peak of capacitance.