Dark current optimization designs for mesa and planar type processed short wavelength infrared photodetectors

Dolaş, Muhammet Halit
This thesis aims to report novel designs to achieve lower dark current values for modified pin heterojunction InGaAs/InP SWIR photodiodes for both mesa and planar type production methodologies.Mesa type studies covernovel passivation methodology based on a fully depleted thin p-InP layer. Mesastructured detectors are targeted due to their competitive advantages for applications such as multicolor/hyperspectral imaging. Test detector pixels with different perimeter/area ratios are fabricated with and without etching the thin InP passivation layer between pixels in order to comparatively examine passivating behavior. I-V characteristics of the test detectors are measured at room temperature. Based on the results from differentlysized pixel groups, bulk and surface dark current components are separated. Results show that thin InP layer decreases dark current by a factor of 3 while increasing photo current due to higher carrier collection efficiencyPlanar type studies withdeveloping novel epilayer structures,junction depth optimization and successful suppression of surface and bulk generation and recombination (GR) dark current components resulted in diffusion current limited high performance planar type SWIR detectors. For 15 μm pixel pitch, we obtained 12fA pixel dark current at room temperature (~26°C) and 1.08 A/W responsivity (at 1.55 μm) that is corresponding 86% quantum efficiency (QE). Dark current modeling analysis is performed based on bias dependency of diffusion, GR and tunneling current components. Results show excellent match with experimental data.Utilizingthe developed planar type detectors with the state-of-the-art performance, post process optimizations also completed which result high performance megapixel SWIR imaging sensorswith record level operability.
Citation Formats
M. H. Dolaş, “Dark current optimization designs for mesa and planar type processed short wavelength infrared photodetectors,” Ph.D. - Doctoral Program, Middle East Technical University, 2021.