Miniaturized InSb mid‐IR photovoltaic sensor for room temperature operation

Abstract

AbstractWe have developed a miniaturized InSb middle‐infrared photovoltaic sensor (InSb PVS) that operates at room temperature. A single InSb photodiode of the InSb PVS consists of an InSb p+‐p–‐n+ photodiode structure grown on a semi‐insulating GaAs (100) substrate, with a p+‐Al0.17In 0.83 Sb barrier layer between p+ and p– layers to reduce diffusion of photo‐excited electrons. The n‐ and p‐type dopants used are Sn and Zn, respectively. To avoid 1/f noise, we operated our InSb photodiode in photovoltaic mode to output an open‐circuit voltage. Moreover, to improve the signal‐to‐noise ratio, 700 photodiodes arranged on a 600 × 600 μm chip were serially connected to each other. We found that the output signal voltage of the sensor depends on the Zn doping concentration in the p– layer. The peak output voltage was obtained at about 6 × 1016 cm–3, which corresponded to the minimum value of the carrier concentration in the p– layer. After packaging, the final external size of the sensor was 2.2 × 2.7 × 0.7 mm. To our knowledge, our sensor is the smallest uncooled sensor in the mid‐IR range reported up to now. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)