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Investigation of the Response Mechanism of a Hg0.46Cd0.54 Photovoltaic (PV) Detector Irradiated by Continuous Wave Sub-bandgap Photons
T. Jiang, X. Zheng, X-A. Cheng, H-M. Jing and Q-S. Lu

We have observed open-circle voltage, Voc, signals in a photovoltaic (PV) Hg0.46Cd0.54Te detector irradiated by the beam of a continuous wave (CW) CO2 laser operating at 10.6 mm and around 50 W/cm2. The photon energy (approximately 0.12 eV) is far less than the band gap (approximately 0.91 eV) of the Hg0.46Cd0.54TeTe detector. The observed signals are attributed to the thermally generated carrier separation by the built-in field. This phenomenon is called the thermovoltaic effect. Temperaturedependent Voc measurements from a Si-solar cell under brand iron heating were in good agreement with the voltage responses of the Hg0.46Cd0.54Te detector irradiated by a CW CO2 laser beam. This work experimentally demonstrates that the response mechanism of the Hg0.46Cd0.54Te PV detector irradiated by CW sub-bandgap photons exhibits a thermovoltaic effect instead of a photovoltaic effect, such as two-photon absorption and multi-photon absorption.

Keywords: Photovoltaic detector (PV), CO2 laser, 1319 nm laser, thermally generated carrier, thermovoltaic effect, photovoltaic effect, sub-bandgap photon

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