Vertical Piezo-Optoelectronic Coupling in a 3C-SiC/Si Heterostructure for Self-Powered and Highly Sensitive Mechanical Sensing

Abstract

This paper presents a novel self-powered mechanical sensing based on the vertical piezo-optoelectronic coupling in a 3C-SiC/Si heterojunction. The vertical piezo-optoelectronic coupling refers to the change of photogenerated voltage across the 3C-SiC/Si heterojunction upon application of mechanical stress or strain. The effect is elucidated under different photoexcitation conditions and under varying tensile and compressive strains. Experimental results show that the relationship between the vertical photovoltage and applied strain is highly linear, increasing under the tensile strain while decreasing under the compressive strain. The highest sensitivities to tensile and compressive strains are 0.146 and 0.058 μV/ppm/μW, respectively, which are about 220 and 360 times larger than those of the lateral piezo-optoelectronic coupling reported in literatures. These extremely large changes in vertical photovoltages are explained by the alteration in effective mass, energy band shift, and repopulation of photogenerated holes in out-of-plane, in-plane longitudinal, and in-plane transverse directions when strains are exerted on the heterojunction. The significant enhancement of strain sensitivity will pave the way for development of ultrasensitive and selfpowered mechanical sensors based on the proposed vertical piezo-optoelectronic coupling.

Photovoltaic Effect-Based Multifunctional Photodetection and Position Sensing Using a 3C-SiC/Si Heterojunction

“…Owing to advanced Si fabrication technologies, one of the most important polymorphs, cubic silicon carbide 3C-SiC has been epitaxially grown on Si wafers (up to 300 mm in diameter). , Thus, cost-effective 3C-SiC/Si wafers have been manufactured commercially to satisfy the requirements of industry and academia. Then, extensive studies on SiC sensing effects have been conducted, such as piezoresistive effect for mechanical sensors and accelerometers, , thermoresistive effect for temperature sensors, , and photovoltaic effect for photodetectors and position sensors. − Furthermore, SiC/Si heterojunctions own a larger valence band offset compared to homojunctions (∼1.3 eV), exhibiting excellent diode characteristics. , SiC/Si heterojunctions fabricated with two dissimilar narrow-bandgap and wide-bandgap semiconductors are also advantageous for absorbing a wide spectrum range . Therefore, SiC/Si heterojunction-based broadband photodetectors have been successfully developed. , Regarding materials for photodetection and photonic devices, other advanced semiconductors have attracted a lot of attention, including two-dimensional (2D) materials (bismuth, selenium, tellurium), perovskites, and other low-dimensional wide-bandgap semiconductors. − …”