Properties of Lead Telluride Mid-Infrared Imaging Devices of Focal Plane Arrays

Abstract

We fabricated p–n-junction-type and Schottky barrier (SB)-type lead telluride (PbTe) mid-infrared focal plane arrays (FPAs) using a flip-chip bonder. The detection wavelength peak of the SB-type FPA shifted from 6.10 μm to 4.95 μm as the ambient temperature was increased from −258.15°C to −148.15°C. At −196.5°C, the detection wavelength peak and cut-off wavelength were 5.68μm and 6.16μm, respectively. The p–n-junction-type FPA yielded the sharpest photoconductivity spectrum among the investigated devices, presumably because of the Tl-related deep levels in its p-type PbTe epitaxial layer. These deep levels absorb the mid-infrared light and cut off the detection wavelength range. Thus, the p–n-junction-type FPAs are expected to be employed in vision cameras and sensors with selectable mid-infrared wavelengths. Meanwhile, the SB-type FPA has a high dielectric constant; consequently, it develops a wide depletion layer that detects a wide range of mid-infrared wavelengths. FPAs based on the PbTe system are potentially implementable in simple, highly sensitive, mid-infrared imaging devices with a wide scan range.