GaGeTe/GaN Heterostructure-Based Photodetector with Wavelength-Regulated Dual-Function of Optical Imaging and Synapse.

A wavelength-regulated photodetector based on a GaGeTe/GaN heterostructure is reported. The potential barrier formed by the type-I energy band alignment effectively suppresses reverse carrier diffusion, reducing dark current to the order of 1 × 10 A. Meanwhile, the proposed GaGeTe/GaN photodetector demonstrates remarkable optoelectronic performance, including high specific detectivity (4.3 × 10 Jones) and rectification ratio (3 × 10). Moreover, the device has a responsivity of 2.2 A/W and significant wavelength-dependent modulation characteristics. Under 355 nm illumination, the device switching speed reaches the millisecond level, which is suitable for optical imaging. When tuned to 400 nm, the significantly prolonged relaxation time of photogenerated carriers closely resembles biological synaptic weight updating, enabling the device to precisely emulate neural behaviors including short-term plasticity, long-term plasticity, paired-pulse facilitation, spike number-dependent plasticity, and spike-time-dependent plasticity. Implemented in neural networks, it achieves 93.8% accuracy in handwritten numeral classification tasks. The photodetector based on the GaGeTe/GaN heterostructure breaks traditional functional limitations of photodetectors, providing new insights for developing multimode functional devices using two-dimensional/three-dimensional heterostructures.