Enhanced optoelectronic properties of bilayer graphene/HgCdTe-based single- a nd dual-junction photodetectors in long infrared regime

Abstract

We present novel p+-bilayer graphene (BLG) and mercury cadmium telluride (MCT)-based single- and dualjunction photodetectors, namely, p+-BLG/n–-MCT and p+- BLG/n–-MCT/n+-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 106 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 (QEext), external photocurrent responsivity, and lowest noise equivalent power of 85.8%, 7.33 A/W, and 4.72 × 10−20 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–-n+ heterojunction, which accelerates the photogenerated electrons resulting in effective photocurrent. It is further demonstrated that the temperature-dependent QEext with values >100% is due to the carrier multiplication effect in BLG.