Effects of photogenerated-hole diffusion on 3C-SiC/Si heterostructure optoelectronic position-sensitive detector

Abstract

Single-crystalline silicon carbide (3C-SiC) has been attracting significant attention in recent years due to its cost-effectiveness and high crystalline quality, mature fabrication techniques on Si-substrate and outstanding mechanical, chemical, and optoelectronic characteristics. Taking advantage of its large built-in potential, a promising application of 3C-SiC on Si (3C-SiC/Si) heterostructure is to develop position-sensitive detectors (PSDs) based on the lateral photovoltaic effect. The lateral photovoltage is generated under non-uniform illumination due to the asymmetry diffusion of photo-induced charge carriers. However, the full potential of 3C-SiC/Si heterojunction-based PSDs has not been elucidated yet. In this study, we investigate the influence of photogenerated hole and its diffusion path length on the sensing performance of the devices in attempts to obtain an optimal design and further pushing the limit of the PSD. Devices with different electrode spacings are fabricated on the 3C-SiC/Si heterostructure, and experiments are conducted under different illumination conditions to determine the position-sensitivity. Devices with short electrode spacings are found to have excellent position-sensitivity with the highest sensitivity of 470 mV mm−1 obtained in a device spacing of 300 µm under 980 nm (1000 µW) laser illumination. The physic mechanism underneath the experimentally observed behaviors are explained based on the generation and separation of electron–hole (e–h) pairs under the illumination, and charge carrier diffusion theory. The findings of this work will provide insights to design highly sensitive PSDs and explore its full potentials.