Electrical and Computer Engineering ETDs

Publication Date

Summer 7-11-2019


Summarized here are the measured radiometric characteristics of three Infrared III-V InAsSb/AlAsSb/InAsSb-based nBn focal plane arrays (FPAs) in the SWIR to MWIR range with cutoff wavelengths of 2.85 µm, 3.3 µm and 4.2 µm at the nominal operating temperature of 150 K. Herein referred to by their respective cutoff wavelengths, the nBn detectors are characterized across the temperature range of 130 K to 180 K. The optical response and noise characteristics are examined as a function of cutoff wavelength, and a comparison of dark current density is made to HgTeCd photodiodes using the Rule ‘07 heuristic.

The 2.85 µm, 3.3 µm and 4.2 µm nBn detectors demonstrated quantum efficiencies of 25%, 68% and 82% respectively at the nominal operating temperature of 150 K. The relatively low quantum efficiency observed on the lower cutoff wavelength detectors suggests a lower carrier lifetime due to an increased number of mid gap trap states. Other radiometric metrics such as noise equivalent irradiance (NEI) and responsivity are analyzed as a function of temperature and detector bias, and noise models are created to quantize the effect of various noise components on the overall performance of the detector. An Arrhenius analysis of the dark current data is performed and the activation energies for the nBn detectors provide insight into the dominant dark current mechanisms and possible detector defects, such as the existence of a depletion region in the lower cutoff detectors and the existence of a valence band offset in the 4.2 µm detector. The III-V nBn detectors displayed higher dark current densities compared to their theoretical HgCdTe counterparts, especially at low temperatures. However, results indicate an ongoing improvement in III-V nBn dark current compared to previous years. In all the metrics considered, a lower cutoff wavelength was associated with a decrease in performance for the nBn detectors, except for the bias operating range where the 4.2 µm cutoff FPA displayed more stringent biasing requirements compared to the lower cutoff FPAs.

Document Type




Degree Name

Electrical Engineering

Level of Degree


Department Name

Electrical and Computer Engineering

First Committee Member (Chair)

Ganesh Balakrishnan

Second Committee Member

Payman Zarkesh-Ha

Third Committee Member

Jane Lehr

Fourth Committee Member

Christian Morath