Study On Photoelectric Performance Simulation And Structure Optimization Of InGaAs Detector

The short wavelength infrared(SWIR) InGaAs detectors have significant valuable application in the aerospace remote sensing for their good performance at room temperature. To further enhance the performance of SWIR InGaAs detectors,the influence of lattice matching and extended wavelength detector structure key parameters with In AlAs cap layer on the dark current, and these detectors were verified by experiment and the dark current mechanism of detector were obtained.Then the optimized structure parameters to lower dark current were obtained by simulating the dark current characteristics of detector with electron blocking layer in its absorption layer and without electron blocking layer. Further optimization on the position and period of electron blocking layer was studied.The process of establishing simulation modeling was summarized, including module selection, structure definition, physical model set, numerical method selection, device characteristics and result analysis. In addition, there is a real-time output window which can be used to view the results and parameters of debugging model directly. The general simulation process based on the Atlas software was established.The dark current mechanism of the detector whose In AlAs cap layer is matched with InP substrate was studied by Atlas. The influence of absorption layer thickness and doping concentration on dark current was analyzed. The results indicate that dark current decreases with the increase of thickness of the absorption layer when the thickness is less than 0.25μm. However when the thickness is exceed 0.25μm, there is no obvious changes of dark current. Dark current decreases with the increase of doping concentration, while when the concentration increases to a certain degree, it will affect the light absorption efficiency.The I-V curves were analyzed, and it was found that diffusion current is the main source of dark current at room temperature.With the method of standard substitution, the response spectra of the detectors were sudied. The spectrum were measured and calibrated by grating spectrometer and Fourier spectrometer. Research results show that the standard spectrum device and its standard spectrum can be used to calibrate the spectral response of the device under test. Because of its portability and strong signal and high stability, Fourier spectrometer generally obtained results are better than the grating spectrometer.The dark current mechanisms of the extended wavelength detectors with In AlAs cap was simulated by Atlas, the effects of absorption layer thickness and doping concentration on dark current was analyzed, InGaAs detector based on digital grading super lattice structure(DGSL) was developed, and the dark current and spectral response were measured. The response spectrum is consistent with the simulation results. In terms of dark current characteristics, at-0.01 V, dark current is 6.47×10-9A and 1.05×10-12 A at 300 K and 200K; and studied on the current-temperature characteristic, obtained the activation energy, Ea=0.38 eV at 220K-300 K. The results indicate that the diffusion current and generation-recombination current are the main soure of dark current at room temperature.The analytic results are consistent with the simulation results.The design of inserting an electronic barrier layer into absorption layer is a method to suppress the dark current of detectors. This method can change the carrier transport and reduce the stress and the defect density caused by lattice mismatch. This paper developed D2 device containing electron blocking layer firstly, tested the dark current at room temperature and low temperature, and compared with D1 device without electron blocking layer. The results show that the dark current of D2 is less than D1, at-0.01 V. The dark current of D1 and D2 are respectively 8.27×10-4A/cm2 and 3.25×10-4A/cm2 at room temperature. And it is consistent with the simulation results. The dark current of D1 and D2 decreased with the decrease of temperature, and the decline of them are consistent. The reason is that barrier is formed in conduction band by electron blocking layer, electron transport is impeded, while there is almost no barrier effects in the valence band, so the electron blocking layer extends the life of minority carriers, inhibits the recombination current. Secondly, based on the research above, the simulation technique was used to carry out the research on the optimization of the device structure, analyzed the effects of the position and periodic of superlattice barrier layer on dark current. It is found that lower dark current can be realized when the electron blocking layer is close to the middle of the absorption layer and the periodic thickness is 15 nm.