The Concept of Pressure-Induced Conduction Band Mismatch in Soft–Hard Semiconductors for Self-Powered Phototronic Pressure Sensing

Self-powered pressure sensors are essential devices for health care monitoring, human-machine interface, and robotics in this era of the Internet of Things. Self-powered phototronic mechanical sensors typically utilize piezoelectric materials, such as ZnO, wherein stress-induced charges alter the energy barrier height at the interface of two contacting materials. However, relying solely on piezoelectric materials could restrict the further development of high-sensitivity sensors due to the screening effect, which requires exploration of sensing mechanisms beyond those materials. This study introduces the concept of conduction band mismatch in soft-hard cubic-silicon carbide (3C-SiC) semiconductors, which controls charge transport in SiC nanomembranes under light illumination for self-powered phototronic pressure sensing. The concept is verified through mechanical simulation and experimental results under different light-illuminating conditions and varying pressure levels. Utilizing this concept, supported by aligned carbon nanotube (ACNT) nanofilms acting as a hole collector, the photovoltage generated in 3C-SiC/ACNTs becomes highly sensitive to pressure. The 3C-SiC/ACNTs pressure sensor exhibited a decent sensitivity of 35 mV/MPa, two to six times higher than that of ZnO/Si and Si/SiC devices. The sensitivity is also tunable by light intensity and independent of the pressure direction. The underlying physics is the pressure-induced tensile strain in 3C-SiC that alters its conduction band profile and causes photogenerated electron redistribution. This study can advance phototronics technologies for ultrasensitive, self-powered pressure sensors.