| Infrared detection technology is widely used in military imaging,environmental,medical and other fields.Compared with the commonly used infrared detection materials Mercury Cadmium Tellurium(MCT),In As/Ga Sb type-? superlattice(T2SL)materials have the advantages of high uniformity,high quantum efficiency,small effective mass of electrons and low tunneling current.Theoretically it can achieve higher detection capability and detection temperature.However,there is a large gap between the actual performance and theoretical results of In As/Ga Sb type-? superlattice detectors,mainly due to the existence of various defects in the superlattice structure.the type of defects,the location of these defects,and the impact of the device.However,some key problems,such as defect type,defect location,defect influence on dark current and device noise,have not been solved.In this paper,the photoelectric and noise characteristics of In As/Ga Sb type-? superlattice mid-wave and long-wave infrared detectors are studied.The dark current generation mechanism directly related to the noise in the medium and long wave detector is revealed.The noise source and the noise mechanism in the detector are analyzed through the noise spectrum.Finally,the specific leakage path of the noise is obtained through the photocurrent response graph,and the improvement plan of body craft and surface craft are proposed.The main research contents and results are as follows:1)Research on the photoelectric and noise characteristics of the(13.3ML)In As/(7ML)Ga Sb T2SL long-wave infrared detector.In As/Ga Sb T2SL long-wave infrared detector is prepared by MBE,and its absorption region is the light p-type superlattice layer of 13.3ML In As/7ML Ga Sb with 400 cycles.The relative spectral response of the long-wave infrared unit detector shows that the 50%cut-off wavelength of the detector is 9.3?m and the 100%cut-off wavelength is 11.7?m,which meets the design expectations.The dark current test system shows that in the temperature range of 90?110 K,the main generation mechanism of dark current is the Shockley-Hall-Read generation current and diffusion current.In the temperature range of 65?90 K,the main generation mechanism of dark current is the shunt current and trap-assisted tunneling(TAT)current.By fitting the noise power spectral density of the detector at 77k,the results show that the TAT current dominates the 1/f noise at high reverse bias(greater than-0.1 V),while the shunt current is at low reverse bias(less than-0.1 V).By fitting,the shunt noise coefficient?shunt is 5×10-8,and the shunt resistance Rshunt is 30k?.The measurement of the photocurrent response graphs of the device at different temperatures shows that the dark current and noise generated by the shunt process all originate from the leakage path around the electrode sidewall.The key to further improving the performance of the detector is to suppress the intermixing of atoms and side leakage.2)The material properties and photoelectric properties of the(9ML)In As/(9ML)Ga Sb T2SL mid-wave infrared detector are studied in detail.In As/Ga Sb T2SL mid-wave infrared detector is prepared by growth of MBE technology,and its absorption region is the superlattice layer of 9ML In As/9ML Ga Sb with 300 cycles.The Raman technique is used to characterize the crystal quality of the superlattice,and it is found that the crystal quality of the superlattice is good,and no interface mode was found.The dark current test system is used to analyze the generation current as its dominant dark current mechanism.The test results of variable pressure noise at operating temperature show that the main noise limiting D*is 1/f noise,which may be derived from the surface state of the superlattice.The scanning photocurrent response test shows that the detector has a strong photoresponse at excitation wavelengths of 4?m and 4.2?m,but there are side leakage channels. |
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