| Accompanied by the technological development and extensive applications of infrared focal plane arrays,a new generation of high-performance Hg Cd Te infrared focal plane array(IRFPA)with the characteristics of low cost,low noise,high sensitivity,high temperature work,very long wave detecting and its related diagnostic technology is the main target of the development of infrared technology.It includes high-precision laser beam induced current(LBIC)diagnostic technology,high-sensitive avalanche photodiode(APD)detector,very long wavelength infrared(VLWIR)detector,high operating temperature(HOT)detector.In this paper,LBIC detection platform was set for the study of related preparation technology's influence on device performance.Besides,the research of Hg Cd Te APD,VLWIR detector,HOT detector was developed in both theory and experiment,which aims at providing theoretical guidance and practical experience for the research and development of cutting-edge Hg Cd Te IRFPA systems.The research and results are as follows:1.We report on the disappearance of the photosensitive area extension effect and the unusual temperature dependence of junction transformation for mid-wavelength,n-on-p Hg Cd Te photovoltaic infrared detector arrays.The n-type region is formed by B+ ion implantation on Hg vacancy-doped p-type Hg Cd Te.Junction transformations under different temperatures are visually captured by a laser beam induced current microscope.A physical model of temperature dependence on junction transformation is proposed and demonstrated by using numerical simulations.It is shown that Hg-interstitial diffusion and temperature activated defects jointly lead to the p-n junction transformation dependence on temperature,and the weaker mixed conduction compared with long-wavelength Hg Cd Te photodiode contributes to the disappearance of the photosensitive area extension effect in mid-wavelength Hg Cd Te infrared detector arrays.2.Experimental results of temperature-dependent signal inversion of LBIC for femtosecond-laser-drilling-induced junction on vacancy-doped p-type Hg Cd Te are reported.LBIC characterization shows that the traps induced by femtosecond laser drilling are sensitive to temperature.Theoretical models for trap-related p-n junction transformation are proposed and demonstrated using numerical simulations.The simulations are in good agreement with the experimental results.The effects of traps and mixed conduction are possibly the main reasons that result in the novel signal inversion of LBIC microscope at room temperature.3.Based on the Okuto–Crowell avalanche model,an efficient physical model has been obtained by concerning the major generation-recombination processes,such as trap-assisted tunneling(TAT)and band-to-band tunneling(BBT)recombination.Simulated current–voltage characteristics were in good agreement with available data in the literature,which demonstrates the validity of the proposed model.The origins of dark current in high reverse voltages are jointly dominated by BBT and the avalanche mechanism.It is proved to be effective for reducing BBT by improving the uniformity of the electric field distribution across the junction.The electric performance of p-i-n e-APD can be improved by optimizing the APD structure,such as eliminating the sharp corners of junctions,light doping,and the appropriate thickness in multiplication region.The research has guided the preparation of Hg Cd Te APD,and found out that overhigh concentration of i-type area was the cause of device poor performance.4.Long-wavelength Hg1-x Cdx Te(x?0.219)infrared photodiode arrays are reported.The variable-area and variable-temperature electrical characteristics of the long wavelength infrared photodiodes are measured.An enhanced physical model associated with surface recombination and tunneling effects is developed and numerically demonstrated for analyzing the leakage current mechanism and nonuniformities of long-wavelength Hg Cd Te infrared photodiode arrays.Variable-area results of the Hg Cd Te infrared photodiodes in the arrays is experimentally measured,and analyzed by the numerical simulation associated by including the surface recombination effect,which provides critical information useful in separating surface or bulk effects and evaluating the quality of the surface passivation(S0?2.5×104cm/s).Analysis of I–V characteristic of two typical pixels indicates that the TAT effect dominates the dark current at 50 K,whose strength can result in the nonuniformities of Hg Cd Te infrared photodiode arrays.The trap density of different pixels(approximately 1013~1014 cm-3)with an ionized energy of 30 me V is obtained by using the extracted simulation data.5.The Hg Cd Te PB?n(? represents p-type absorption layer)long-wavelength infrared detector based on bandgap-engineering is designed and validated by the preliminary experiments.Numerical simulation was applied to calculate the current-voltage(I-V)characteristic and zero bias resistance-area product(R0A)for PB?n detectors and traditional pn photodiodes.The results show that the performance of PB?n detector was significantly improved compared with that of conventional pn photodiodes.The design of PB?n barrier structure can essentially reduce the dark current,while significantly improving the responsivity.In addition,when reverse biased,optimized PB?n device can also suppress Auger processes in the absorption layer under the high temperature up to 215 K. |
PDF Full Text Request