Enhanced Optoelectronic Properties of Bilayer Graphene/HgCdTe-Based Single- and Dual-Junction Photodetectors in Long Infrared Regime

Abstract

We present novel p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -bilayer graphene (BLG) and mercury cadmium telluride (MCT)-based single- and dual-junction photodetectors, namely, p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -BLG/n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> -MCT and p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -BLG/n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> -MCT/n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -MCT, operating in long infrared regime. The optoelectronic characterizations utilizing Silvaco Atlas TCAD are validated by analytical modeling. All the devices demonstrate self-powered mode operation and exhibit more than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> times enhancement in photocurrent density. The dual-heterojunction photodetector demonstrates rapid photocurrent switching with the rise and fall time of ~0.05 and ~0.013 ps, respectively, than that of single-heterojunction-based photodetectors. The highest external quantum efficiency (QE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ext</sub> ), external photocurrent responsivity, and lowest noise equivalent power of 85.8%, 7.33 A/W, and 4.72 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-20</sup> W, respectively, are found for the dual-heterojunction photodetector with a wavelength of 10.6 μm at 77 K. Such optimum photodetection performance is attributed to the presence of a huge amount of electric field (180 kV/cm) at n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> -n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> heterojunction, which accelerates the photogenerated electrons resulting in effective photocurrent. It is further demonstrated that the temperature-dependent QE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ext</sub> with values >100% is due to the carrier multiplication effect in BLG.