Applied To The Surface Of The Quantum Well Infrared Detector Plasma Enhanced Coupling Grating Is Studied

Quantum Well Infrared Photodetector(QWIP) as a new topic in the development of infrared detector, has began from1990s. The detection wavelength for QWIP can be adjusted by means of changing the components of Al, and the height of potential barrier and well. Optical transition occurs in different sub-band which belongs to the same band. That is the extrinsic photoconduction mechanism essentially. In addition to its wide wavelength adjustment, it still can use broadband materials (such as GaAs/AlGaAs, etc) to make, with the larger flexibility for material selection. Because the transition within the same conduction band (or valence band) between different sub-bands rely on the direction of light polarization field closely. Thus it is a main problem for this type of detector. Therefore, it becomes one of the important research directions of the quantum well infrared detectors so as to make more incident light to be coupled into quantum well and generate more effective electricity vector which can arouse the ground state electron.After decades of development, a number of coupling method appeared so far, including (1)450optical waveguide or Brewster incident angle,(2) corrugated coupling,(3) random reflection grating, and (4) the coupling grating, including one-dimensional and two-dimensional (2D) diffraction gratings. In this paper, we focus on a new type of2D grating for the purpose of achieving higher coupling efficiency, namely the metal grating. The metal grating is developed by means of employing metal and semiconductor materials as well as metals cycle of arrays. The configuration can realize material dispersion of the cycle structure for which incident light can make free electrons of the metal arousing resonance, so as to form the Surface plasma wave (SP wave).This paper aimed at designing a reasonable coupling layer for the infrared detectors in quantum well based on GaN/AlGaN, in order to improve the detection efficiency of quantum well. By tuning structure parameters such as the size, metal thickness, metal type, grating type, and passivation layer thickness of the2D metal grating in both the computational numerical simulation and experiment to achieve the best coupling efficiency for detecting band of3-5μm.Simulation part was carried out using FDTD Solutions software, which is a FDTD algorithm-based calculation method. Because the feature size of the metal grating and wavelength have the same order of magnitude. Maxwell’s equations are considered as different equations in both time and space. FDTD method becomes more appropriate for this approach.The metal grating was made on sapphire substrate in the experiment. The metal grating is separated from quantum well materials. We only used double-sided polished sapphire for the experiment carried out with equipments of stepping projection lithography system, IBE etching metal grating, and PECVD depositing passivation layer. Through the comparison of the response peaks of infrared transmission spectra and reflective spectra with various parameters, we derived the most suitable parameters for the detected demand.The infrared transmission spectrum was obtained by the Fourier infrared spectrometer. And then compared it with the simulated spectrum calculated before, we attained the best grating size eventually.