Fabrication And Photoelectric Characteristics Of Three-dimensional Tubular Quantum Well Infrared Photodetector

Infrared detection is an important research direction of modern detecting technology,expanding the horizons that human learn about nature and the universe.The infrared detector as one core technology has been developed for nearly two hundred years.By 1980 s,a classic GaAs/AlGaAs quantum well infrared photodetector(QWIP)emerged and developed rapidly.Then,it showed great and broad application prospects in the fields of national defense,aerospace,astronomical observation,civil and so on.The QWIP works based on the intersubband transition(ISBT),and owns the advantages of mature material-growth and device-fabrication technology,good uniformity over large area,high yield rate,fast response and so on.However,it also has the disadvantages of small quantum efficiency(QE),low working temperature and non absorbing vertical incident light(N-tpye).So,how to improve the performance has become a key research subject of the QWIP.By now,the means of electronic state regulation,such as optimizing electronic transport and adjusting working mode,has reached the limit.But,the way of light field regulation,such as using the optical coupling structure to enhance QW light absorption,is developing.In this paper,a three-dimensional(3D)tubular QWIP is proposed and studied.The details are as follows:1.The material,structure and manufacturing process of the 3D tubualr QWIP are designed,and the device is fabricated.The numerical simulation method is used to analyze the electromagnetic coupling of tubular structures for determining the device size.Then,different functional layers of material are designed,including the QW structure.Next,the device process flow is customized,and the mask plates are made.Finally,after completing each process step the tubular device is fabricated.2.The optical coupling and response characteristics of 3D tubular QWIP are studied.We fabricate a tubular device with the peak response wavelength of ~ 6.5 ?m,in the conditions of 60 K and 0.65 V who has the peak photocurrent responsivity of ~381 mA/W,corresponding to the QE ~7.2%.By comparing with the 45 o edge-facet device,it is found that the tubular structure achieves a 3 times enhancement of the responsivity and QE.The reason is that part of incident light is confined in the tubular cavity and forms multiple internal reflection to promote the embedded-QW light absorption.The blackbody responsivity of the tubular device under different incident angle of the external light was measured.Result shows that the 3D tubular QWIP exhibits a wide-angle optical coupling characteristic caused by the circular symmetry of spiral microtube.In addition,the effect of the rolling number on the device performance is also investigated.3.The effect of the variation of membrane stress states on the ISBT of QW in 3D tubular QWIP is analyzed.By measuring the photocurrent spectrum of the planar and tubular devices,it is found that the relaxation of strained nanomembrane leads to a tiny redshift of the peak response wavelength.Theoretical analysis shows that when the planar strained nanomembrane rolls up into the microtube,the change of the stress state inside the tube wall causes the QW conduction-bandedge shift,and further result in the shift of response spectrum from the ISBT.At the same time,the photocurrent spectra of the device under different biases was measured.The result shows that the external electric field causes the blueshift of response spectrum,which is related to the quantum confined Stark effect(QCSE)of the symmetric QW,and finally the calculated value is in accord with the experimental result.In order to further improve device performance,a 3D tubular resonant cavity QWIP is designed.Based on the resonant effect,some optical resonance modes are formed in the tube wall,whose intense light field can significantly enhance the QW optical absorption.Simulated results show that when the resonant wavelength of the microtube is located in the QW absorption range,there will be a series of spikes superimposed on device response spectrum,and these spikes have a high-Q value.