| With the rapid development of new information technology,researchers pay more and more attention to the photoelectric devices with high response,small volume and low noise.Optoelectronic technology involves the radiation,transmission and energy conversion of light,and as one of the important applications of optoelectronic technology,photodetector has been widely used in national defense and civil industry.At present,most semiconductor materials are difficult to adjust the response spectrum and require a large volume of low-temperature refrigeration system for normal operation,which is not conducive to the miniaturization of devices.Hot electron detector based on plasmon resonance can not only greatly improve the efficiency of the device,but also solve the defect that the device is not conducive to miniaturization due to the need for refrigeration.However,the current research on hot electronic devices is mainly confined to the visible and near-infrared band,and there are few literature reports on the research and design of hot electronic devices in the mid-infrared band,and the research on the resonance mechanism of devices is lacking.The effective generation and transfer of thermo electrons is directly related to the material properties and structure of the device.It is of great theoretical significance and potential engineering application value to explore the photoelectric conversion process and loss mechanism of thermo electronic devices in mid-infrared.The main research contents of this topic are as follows:Combined with the open source electromagnetic field calculation software package Meep,the optical structure optimization design of the two-dimensional Al/GaAs stacks hot electron device and the three-dimensional fishing net hot electron device are carried out based on the elite reservation genetic algorithm,and the high optical response characteristics under normal incident are realized.At the same time,the optical absorption characteristics of the device under different oblique incidence angles are investigated,and MLC equivalent circuit model is established to explain the mechanism of device resonance mainly due to the interaction of magnetic polarization between layers and surface plasmons.The optimized two-dimensional stacks structure can achieve the hyperspectral absorptivity of 0.9991 at the target band of 4μm,and the quality factor Q is 22.32,which reaches a higher level than the existing literatures.However,under the condition of oblique incidence,the optimized two-dimensional narrow-wave thermoelectronic device can only make the spectral absorption of the target wavelength reach more than 0.85 within the range of±30°.The optimized wide-wave thermoelectronic device generates four formants in the 3-5μm band,and the average spectral absorption rate is 0.6085.The average absorption rate of the device does not change basically,and still can maintain the average absorption rate of about 0.61.On the basis of reducing the complexity of the device,the optimized three-dimensional fishnet structure achieves a better absorption rate of the normal incidence spectrum than that of the two-dimensional narrow-wave thermoelectronic device.The spectral absorption rate at the target wavelength of 4μm is 0.9996,but it can only guarantee the target wavelength spectral absorption rate close to 1 in the oblique incident range of±15°.The electrical response characteristics of two dimensional stacks and three dimensional fishing net thermoelectronic devices are calculated,the influence of applied bias voltage on the electrical response characteristics of thermoelectronic devices is explored,and the influence mechanism of applied voltage on the electrical response is explained.When the target wavelength is 4μm at 1V/m,the photocurrent of the two-dimensional laminated-narrow-wave thermoelectronic device is Iph=0.217nA/m and the corresponding electrical responsivity is R=109.23mA/W,considering the multiple reflections of high-energy hot electron in the Al thin layer.Compared with the results in the control literature,The two-dimensional hot electron device designed in this paper realizes the detection capability of the farther band,and the responsiveness is improved by 15.56%.When the target wavelength is 4μm and the power is 1W,considering the multiple reflection of high-energy thermelectrons in the Al thin layer and the thermal electron energy distribution of the material,the photocurrent IPh of the three-dimensional fishing net thermonic device is 157.05m A,and the corresponding electrical responsivity R=157.05mA/W.Compared with the narrow-band detector with two-dimensional Al/GaAs grating structure,the structure complexity is reduced and the detection responsiveness R is increased by 43.78%under the condition that the target wavelength absorptivityαand quality factor Q are almost unchanged.It takes-0.18V for the hot electrons generated in Al to have the energy needed to cross the barrier.With the increase of external bias Vapp,the detection responsiveness R of the device also gradually increases.When Vapp=0.1V,the responsiveness of both 2D and 3D thermoelectronic devices can be improved by nearly 6 times compared with that of non-biased devices.The energy dissipation mechanism of hot electron detector is investigated.For wide band hot electron detector,energy loss is mainly focused on the light reflection and transmission,the two-dimensional Al/GaAs stack broadband detector reflecte nearly 40%of the energy,narrowband hot electron detector can improve light absorption characteristics of the device to near 0.999 through structural optimization.In the electrical response characteristics,the loss mechanism of the device mainly lies in the thermalization of hot electrons.The hot electrons which are not transferred to the semiconductor within 1ps will transfer energy to the crystal lattice.When 4μm light wave incidents into Al material,only 88.45%of the generated hot electrons can be emitted and transferred,and 11.55%of the generated hot electrons will be lost because the momentum is too small.Reasonable selection of materials for thermoelectronic devices and reduction of the interface barrier by forward bias voltage are effective methods to solve the electrical response loss.In this paper,the genetic algorithm is used to optimize the Al/GaAs hot electron devices.The photoelectric response characteristics of the two-position lamellar and three-dimensional fishnet thermoelectronic devices are studied and the resonance mechanism is explained.In this paper,an attempt is made to design a mid-infrared hot electron detection structure with better photoelectric response.This will have important theoretical significance and potential engineering application value for the research of new type detector. |
