Infrared detector activities at NASA Langley Research Center
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Infrared detector activities at NASA Langley Research Center M. Nurul Abedin1, Tamer F Refaat2, Oleg V Sulima3, and Farzin Amzajerdian4 1 RSFSB, NASA LaRC, 5 N. Dryden St., Hampton, VA, 23681 2 Old Dominion University, Norfolk, VA, 23529 3 University of Delawrae, Newark, DE, 19716 4 NASA LaRC, Hampton, VA, 23681 ABSTRACT Infrared detector development and characterization at NASA Langley Research Center will be reviewed. These detectors were intended for ground, airborne, and space borne remote sensing applications. Discussion will be focused on recently developed single-element infrared detector and future development of near-infrared focal plane arrays (FPA). The FPA will be applied to next generation space-based instruments. These activities are based on phototransistor and avalanche photodiode technologies, which offer high internal gain and relatively low noise-equivalent-power. These novel devices will improve the sensitivity of active remote sensing instruments while eliminating the need for a high power laser transmitter.
INTRODUCTION NASA’s Earth Science Technology Office and Science Mission Directorate show great interest in broadband detectors for numerous critical applications such as temperature sensing, process control, and atmospheric monitoring of trace gases (CO2, H2O, CO, and CH4). When selecting a detector for such applications, key parameters, must be considered in order to satisfy the requirements of the Earth and planetary remote sensing systems. These parameters include spectral response, quantum efficiency, noiseequivalent-power (NEP), and gain. In general, large format focal plane arrays (FPA) in the 1.0 to 2.5 µm spectral range are the detectors of choice for the next-generation Earth and Space Science remote sensing, Mars Orbiter, and planetary instruments. An Antimonide (Sb)-based heterojunction phototransistor (HPT), as a suitable candidate, stimulates a strong interest for broadband remote sensing applications [1-4]. Besides p-i-n photodiodes and avalanche photodiodes (APD), HPTs have also attracted a great attention to satisfy many of the detector requirements for these applications without excess noise and high bias voltage problems, while maintaining superior NEP. HPT has an internal gain mechanism that allows increasing the output signal and signal-to-noise ratio (SNR). However, further reduction of gain related noise is desirable, and research on different HPT structures indicate some important design considerations that can minimize device noise and further increase the SNR. On the other hand, APDs are integrated solid-state semiconductor devices that manufactured using different materials. The common near-IR InGaAs/InP APDs are operational in the spectral range of 0.9 to 1.6 µm [5-7]. Recently, a group from DRS Technologies demonstrated responsivity of ~ 15 A/W using HgCdTe electron (e-) APD at
short wave infrared (SWIR) wavelength (at -7 V and 20oC) [7]. However, HgCdTe eAPDs have demonstrated very high responsivity in the 3.0 to 5.0 µm range and their SWIR respon
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