Spatially resolved optoelectronic puddles of WTe2–2D Te heterostructure†

Two-dimensional (2D) semiconductors have attracted significant scientific interest because of their optical properties. Their applications in optoelectronic devices can be further expanded by combining them to form heterostructures. We characterized a WTe₂–2D Te heterostructure through local probing of the photocurrent with respect to the magnitude, phase, and position. Photocurrent generation within the device is divided into distinct regions: photo-thermoelectric effects occur solely at the 2D Te–Au junction area, PV-dominant effects at the 2D–WTe₂ interface, and thermoelectric-to-photovoltaic crossover effects at the WTe₂–2D Te overlap area. These different photocurrents cannot be fused into a single domain because each area is governed by different generation mechanisms, which depend on the location of the device. The power dependence of each photocurrent type also varies within the device. Our results indicate that careful material selection and device structure design, based on the electronic, optical, and thermal properties of the channel materials, are essential to avoid forming different optoelectronic puddles that could counteract each other within a single device.