Broadband and Flexible Photodiode of a Bromine-Doped Lateral MoTe2 Homojunction

The implications of atomically thin-layered two-dimensional (2D) materials for electrical, optical, and flexible applications have great potential for a new-generation technology. Here, we successfully fabricated a flexible and lateral homojunction photodiode using a single molybdenum ditelluride (MoTe2) flake with varying thicknesses (thin–thick). The gate voltage manipulation allowed a significant separation of photocarriers and created a built-in field at the interface, resulting in broadband photodetection from ultraviolet to near-infrared wavelengths. The study found that thin-MoTe2 and thick-MoTe2 act as strongly p- and n-type semiconductors, respectively. The effect of bromine (Br) on the MoTe2 surface showed efficient p-type doping on thin-MoTe2, leading to an improved current rectification ratio. The rectification ratio of the pristine device (1.18 × 103) increased by the order of 102 after bromine adsorption (4.66 × 105) at Vg = −20 V. The gate-tunable photodetection of the lateral homojunction MoTe2 diode demonstrated remarkable photoresponsivity (58.4 AW–1), external quantum efficiency (19,840.95%), and detectivity (2.53 × 1011 Jones). We also successfully demonstrated the fabrication of the homojunction MoTe2 photodiode on a flexible substrate, holding promise for wearable medical optoelectronic devices. Performance evaluation under different bending radii showed slightly reduced responsivity (25.4 AW–1) compared to that of the flat surface (27.3 AW–1). Thus, this research presents an intriguing approach for high-performance and flexible photodetectors based on MoTe2 lateral homojunctions, with potential applications in optoelectronics and future wearable technology.