Research on broadband heterojunction phototransistor based on low-dimensional nano materials

Abstract

Ultraviolet to infrared broadband spectral detection capability is a technological challenge for sensing materials being developed for high-performance photodetection. In this work, we stacked 9-nm-thick tellurium oxide (TeOx) and 8-nm-thick InGaSnO (IGTO) into a heterostructure at a low temperature of 150 ℃. The superior photoelectric characteristics we achieved benefit from the intrinsic optical absorption range (300–1500 nm) of the hexagonal tellurium (Te) phase in the TeOx film, and photoinduced electrons are driven effectively by band alignment at the TeOx/IGTO interface under illumination. A photosensor based on our optimized heterostructure exhibited a remarkable detectivity of 1.6x1013 jones, a responsivity of 84 A/W, and a photosensitivity of 1x105, along with an external quantum efficiency of 222 % upon illumination by blue light (450 nm). Simultaneously, modest detection properties (responsivity ~31 A/W, detectivity ~6 x 1011 jones) for infrared irradiation at 970 nm demonstrate that this heterostructure can be employed as a broadband phototransistor. Furthermore, its low-temperature processability suggests that our proposed concept might be used to design array optoelectronic devices for wideband detection with high sensitivity, flexibility, and stability. Broadband phototransistors have attracted a considerable attention for widespread applications. Amorphous oxide semiconductor (AOS) based transistor provides an excellent photo-sensor platform because of its reasonable high mobility, extremely low off-state current, low-cost fabrication capability and large area scalability. To offer a photoresponsivity for visible to infrared light in AOS transistor, lead sulfide quantum dots (PbS QDs) with cutoff wavelength of 1300 nm was introduced using spin-cast where the inter-distance between PbS nano dots was tailored by the shorter tetrabutylammonium iodide ligands through a ligand-exchange process. To reduce the operation voltage of oxide phototransistor, the indium gallium oxide (IGO) and hafnium oxide (HfO2) films were used as the semiconducting n-type channel and gate insulator, respectively, which were grown by plasma-enhanced atomic layer deposition (PEALD) route. The fabricated PbS QD/IGO phototransistors with HfO2 gate insulator exhibited the remarkable switching properties such as high carrier mobility of 20.1 cm2/(Vs), low subthreshold gate swing of 0.060 V/decade, high ION/OFF ratio of 2.2 × 108. and SS = 0.06 V/dec even at an ultralow power operation (VGS = ±1 V, VDS = 0.1 V). In addition, they exhibited an unprecedented excellent performance with a photoresponsivity values of 211 A/W and detectivity of 8.9 × 1011 jones under infrared region of 1300 nm. The relevant physical rationale is discussed on the structural, optical and electrical analysis. This result suggests that the phototransistor with PbS QD/IGO/HfO2 stack can provide the large area scalable, low-voltage operation routes for visible-to-infrared imaging, communication and sensing applications.