| Tellurium cadmium mercury(MCT)infrared detectors typically require liquid nitrogen refrigeration to suppress dark currents and obtain high detection sensitivity and signal-to-noise ratio.However,refrigeration equipment induces problems of high power consumption,large size and high cost,which limit the applications of infrared detector.The development of optical and electrical coupling detector is an effective strategy to reduce the intrinsic dark current of photodetectors and improve detection performance,and thus to achieve high operating temperature detection and lower the requirement of refrigeration equipment.The key to the technique is to enable the sub-wavelength thickness absorbing material to absorb enough photons to produce a sufficiently large photocurrent.This paper combined the optical microcavity and antenna to construct a SPR enhanced MCT microcavity infrared detector with a wide response range and high light absorption.The thickness of the absorbing layer is sub-micron scale,which could effectively suppress the dark current of the device and improve the infrared detectivity.The main research contents are as follows:(1)The contribution of plasmon resonance enhancement,microcavity effect and coupled resonance of plasmon and microcavity to broadband MWIR detection performance was studied through Finite-Difference-Time-Domain.Metal antennas and microcavity were well designed to induce resonance coupling,to achieve high absorption over a wide range in MWIR.For microcavity resonance wavelength at 3.45 μm,high absorption efficiency of 95.3% was abtained in the proposed structure with the MCT thickness of 530 nm,with the broadband FWHM of 1.33 μm.(2)The photoelectric conversion performance of the optimal SPR enhanced MCT microcavity detectors was studied by Finite Alement Analysis.The calculated photogenerated carrier rate was used here as input to calculate the photocurrent intensity of the SPR enhanced MCT microcavity detector and the MCT film detector.At 1 V bias,the current of the proposed detector at 3.5 μm was increased by 55% relative to MCT film detector with the same thickness.It showed that the concentration of photogenerated carriers of the SPR enhanced MCT microcavity detector increased significantly due to the increased light absorption,and the collected photocurrent signal was significantly enhanced.To achieve such high response,the thickness of the MCT layer of MCT film detector required to be increased to more than 4 μm.However,the dark current was also correspondingly increased by more than 8 times.(3)The thickness of the cadmium tellurium layer was adjusted to 1100 nm according to the fabricating process conditions of MCT film.The SPR enhanced MCT microcavity detector with the MCT layer thickness of 1100 nm was fabricated by semiconductor process and micro/nanofabrication technologies.The FTIR test showed that the peak absorption efficiency of the prepared SPR enhanced MCT microcavity at 3.6 μm was up to 98.7%,which was 150% higher than that of the MCT film with the same thickness,and the FWHM of was 1.12 μm.It was expected to achieve a broadband high sensitivity response of MWIR infrared detectors. |
