Hypersensitive Optical Position Sensing Enabled by a Double-Heterojunction Nanothin-Film Composite

Sensors capable of detecting the position of light are widely used in measurements of position, angle, distortion, and vibration. They play an important role in various applications, such as imaging, robotics, and optical communication. Here, we present a high-sensitivity light sensor based on a novel triple-layer semiconductor structure, consisting of (1) p-type cubic silicon carbide (p-3C-SiC), (2) p-type silicon (p-Si), and (3) n-type silicon (n-Si). This configuration forms a p-3C-SiC/p-Si/n-Si double junction (DJ), which is systematically compared to a p-3C-SiC/n-Si single junction (SJ) to benchmark their sensitivity performance under nonuniform illumination by scanning a laser beam across two electrodes. The inclusion of a low-doped p-Si layer in the DJ structure leads to a more than 200-fold increase in sensitivity (defined as photocurrent change per unit displacement of the laser spot (A/mm)) compared to the SJ device under optimal bias conditions. Specifically, under a 1.5 V bias, the sensitivity of the DJ structure is 1384 × 10^-6 A/mm, whereas that of the SJ structure is only 5.98 × 10^-6 A/mm. The enhanced sensitivity is attributed to the improvement of charge carrier generation, separation, and transport in the double heterojunctions. Importantly, the DJ structure achieves this excellent performance enhancement without significantly increasing the fabrication cost compared to the SJ counterpart. These results highlight the potential of DJ-based architectures to enhance the sensitivity of optoelectronic sensors, offering new opportunities for advanced PSD applications.