The Design And Characterization Of Suspended Waveguide Photodetector Featuring With GaN Multiple Quantum Wells

As a key device in modern optical communication systems,photodetectors play an important role in promoting the rapid development of social information industry.The integration of photodetectors with waveguides of different structures further facilitates the application of detectors in different fields.Photodetectors with waveguides have many advantages,such as high response rate,high reliability and easy to manufacture.The integration of photodetectors and waveguides will be a promising research direction of future optical communication devices.In this paper,a monolithic integration of suspended waveguide and photodetector is successfully realized on a GaN-on-silicon platform based on the suspended waveguide and photodetector fabrication process.The main work and achievements are as follows:A GaN suspended waveguide is proposed and its optical coupling properties are simulated and analyzed using FDTD numerical method.Due to the high index of the GaN material compared to air,the suspended waveguide achieves highly light-confining ability.The main processes of UV photolithography,deep silicon etching,back thinning etching and electron beam evaporation are studied,and the suspended photodetector with waveguides featuring p-n junction GaN multiple quantum wells is realized.Both deep silicon etching and back thinning etching are conducted to achieve the suspended waveguide.Subsequently,the structure of the device,the electrode region and the surface roughness of the membrane are characterized and analyzed by optical microscope,scanning electron microscope(SEM)and atomic force microscope(AFM).The setup is built for the device characterization.The main characteristics of the device are measured and the results are analyzed.The device exhibits two operation modes.The peak values of the responsivity spectra for the suspended waveguide photodetector locate around 401 nm at 3 V bias(~140 mAW-1)and 435 nm at 0 V(~7.58 mAW-1).In addition,the metallization stacks can serve as a bottom metal mirror to reflect the incoming light back for re-absorption,leading to improved photocurrent response.