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 V_g = −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.