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Congratulations to Dr. Teressa Specht

Congratulations to Dr. Teressa Specht on her successful defense of her dissertation on "Advancements Toward High Operating Temperature Small Pixel Infrared Focal Plane Arrays: 
Superlattice Heterostructure Engineering, Passivation, and Open-circuit Voltage Architecture"!


Dissertation Abstract

Infrared detectors have been steadily evolving since their inception in the 1950’s. Present day imagers consist of staring large format focal plane arrays (FPAs) based on HgCdTe and III-V strained layer superlattice (SLS) material systems. Type II superlattice (T2SL) structures, are emerging as an alternative due to their low Auger recombination, high effective electron mass, and detection tunability across the mid-wave infrared (MWIR, 3-5 μm) and long-wave infrared (LWIR, 8-12 μm) wavelength regions. 

There are several research challenges associated with the development of small detector pixels that can operate at high temperatures for these SLS detectors. In this work, I have identified the scientific challenges limiting current detector technology and investigate the underlying device physics to mitigate poor performance. There are three main contributions of this dissertation: 

Superlattice Heterostructure Engineering: We designed, fabricated, and tested unipolar barrier nBp detectors with InAs/GaSb, InAs/InGaSb, and InAsSb/GaAsSb SLS detectors. 
Suppression of Surface Leakage Current with Passivation: We investigated the use of Al2O3 and ZnO via atomic layer deposition (ALD) to reduce the surface leakage current in LWIR detectors.

Demonstration of an Open-circuit Voltage Photodetector (VocP) Architecture: We re-examined the relative advantages of using the reverse-bias photocurrent of a photodiode versus using the open-circuit voltage under the same conditions. We investigated the detector physics through analytical modeling, fabrication, integration and test of a VocP detector and explored the potential of using this for high operating temperature (HOT) small pixels in FPAs.  

Overall, the results of this research will influence both material system designs and processes and the critical role of the detector to readout integrated circuit (ROIC) interface to push the boundaries of fundamental concepts in infrared detector technology affecting these detectors for future high-density, HOT FPAs.