'Middle East Technical University, Faculty of Architecture'
Abstract
In0.53Ga0.47As is the most appropriate material system for Short Wavelength Infrared (SWIR) detection at ~1.7 μm cutoff wavelength with its relatively lower cost and high performance. Ultra-low dark current (~ nA/cm2) has been recently demonstrated in InGaAs photodetectors with planar type process by eliminating surface leakage current. Here, a fabrication procedure for planar InGaAs photodetectors with unique pixel isolation methods has been developed and ~10 nA/cm2 dark current density levels were obtained from 15 and 25 μm pitch megapixel and large format Focal Plane Arrays (FPA) where almost 100% internal quantum efficiency was measured. Mesa type InGaAs photodetectors were also fabricated to be able to make a comparison between two process types. Developed photodetectors were able to sense both Near Infrared (NIR) and visible region of electromagnetic spectrum by removing InP substrate and ~99.5% pixel operability was achieved in FPAs after flip-chip bonding and substrate removal. Furthermore, a novel all InGaAs nBn photodetector design was also proposed numerically in order to reduce surface leakage current particularly in mesa type photodetectors. Simulations were executed in Sentaurus TCAD numerical tool where InGaAs material properties were optimized with the data provided in literature, and also with the experimental results obtained in InGaAs photodetector fabrication. Shockley-Read-Hall (SRH), Auger, radiative and surface currents were modeled and more than 20 times improvement in dark current has been shown to be achievable by utilizing nBn photodetector compared to conventional p-n InP/InGaAs photodetectors without degrading responsivity.M.S. - Master of Scienc
