Title: Linear Mode Photon Counting HgCdTe Avalanche Photodiode Arrays Sensitive from 0.4 to 4.2 μm for Space Lidar and Passive Spectrometers
Presenting Author: Xiaoli Sun
Organization: NASA GSFC
Co-Author(s): D. Beck, DRS Technologies; James B. Abshire; NASA GSFC

Abstract:
A new type of linear-mode photon counting (LMPC) HgCdTe electron avalanche photodiode (e-APD) array has been developed in partnership with DRS Technologies under NASA Earth Science Technology Office (ESTO) Advanced Component Technology (ACT) program. The LMPC HgCdTe e-APD focal plane array (FPA) consists of an HgCdTe e-APD array and a matching read-out integrated circuit (ROIC) directly under the e-APD to minimize the stray capacitance and reduce the electronics noise. The electrical bandwidth of the FPA is 100-150 MHz, which is sufficient for most of the space lidar and passive spectrometer applications. The outputs of the LMPC e-APD FPA consist of the analog waveforms, one for each pixel, which are linear to the incident light with a wide dynamic range and a noise level well below the single photon pulse amplitude. As a result, each pixel is capable of detecting single to multiple photon events with continuous and liner output. There are no dead-time, afterpulsing, or other nonlinear effects and there is no need for gating. The LMPC HgCdTe e-APD array developed for the ACT program has 2x8 pixels with 22 μm pixel size at 64 μm pitch. Test results show the photon counting efficiency is about 50% at <200 KHz noise count rate at 1.55 μm wavelength. The spectral response of the HgCdTe e-APD extends from 0.4 to 4.2 μm, making them the only single photon detectors from visible to short wave infrared (SWIR) and mid-wave infrared (MWIR) band. We have significantly advanced the infrared detector technology under the ESTO ACT program. DRS Technologies maturated the production process, identified and reduced various noise sources, such as feed back from the ROIC glow, and developed an integrated bias and ROIC control electronics circuit board. One of the LMPC HgCdTe e-APD detectors will be integrated with a closed cycle tactical cooler in a Cubesat and is scheduled to be delivered for launch in mid-2015 under ESTO In-space Validation of Earth Science Technology (InVEST) program. These new LMPC HgCdTe e-APD detectors will greatly improve the receiver performance of space lidar and passive spectrometers under development at NASA and enable new measurements over 0.4 to 4 micron wavelength band.