Optimization of III-V Materials Based Short Wavelength Infrared Photodetectors

Date

2023-6-15

Author

Çırçır, Kübra

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This thesis focuses on the performance enhancement of mesa type lattice-matched InGaAs short-wave infrared (SWIR) photodetector technology by addressing the challenges associated with dark current and electrical crosstalk. Mesa type InGaAs photodetectors offer remarkable features such as high reproducibility, uniformity and compatibility with dual-color photodetector configuration, although there is still an ongoing need for performance improvement, especially in low photon flux conditions. The inclusion of the in-device InP passivation layer to standard mesa type was examined numerically by exploring constructional and electrical parameters. Total dark current was reduced approximately 17 times thanks to the effectiveness of surface-related dark current suppression in comparing the scenarios where the passivation layer was etched and not etched. This mesa-based depleted passivation structure was employed to fabricate a large format (640x512) focal plane array (FPA) with 25 µm pixel pitch. The surface passivation impact was also proven experimentally in comparison with standard mesa type and this effect provides dark current as low as 4.1 µA/cm2 for FPA pixels at room temperature. This result indicates significant potential for further improving the performance of mesa type photodetectors even though it is still higher than the planar type dark current level. In addition, electrical crosstalk degradation of the mesa-based depleted passivation structure due to high electric field formation between pixels is removed by adopting a new epilayer design, named modified depleted passivation structure. Inter-pixel crosstalk for the nearest pixel (NP) was numerically improved from 15.6 % to 0.2 % by manipulating the electric field between the pixels while preserving the dark current suppression capability. After the fabrication of test detectors, the dark current and electrical crosstalk suppression capability of mesa-based modified depleted passivation structure was confirmed by obtaining 14 times lower dark current at room temperature and reduction of crosstalk from 18 % to 6 % for a pixel with 30 µm pixel pitch at barrier biasing voltage (Vb). The measurement of responsivity yields a quantum efficiency of 61 % without using any anti-reflection coating and removing the InGaAs etch stop layer from the backside of the detector.

Subject Keywords

Short-wave infrared photodetector, InGaAs, mesa type, dark current, crosstalk

URI

https://hdl.handle.net/11511/104534

Collections

Graduate School of Natural and Applied Sciences, Thesis