Silicon carbide (SiC) is emerging as a potential material for harsh environment applications owing to its superior electrical and mechanical properties, as well as excellent chemical inertness. Among more than 200 polytypes, single crystalline cubic silicon carbide (3C-SiC) is attracting signi cant research interest due to its higher channel mobility and lower energy bandgap that make it the most suitable polytype for developing electronic and optoelectronic devices. The 3C-SiC lms are usually grown on 4H-SiC, 6H-SiC, and Si-substrates due to the lack of 3C-SiC-substrate. Unlike other 3C-SiC heterostructures, 3C-SiC/Si is the preferable heterojunction for Micro/Nano-Electro-Mechanical Systems (M/NEMS) applications as it can be grown on commercially available large Si-wafers, and hence the cost of wafers reduces significantly. However, most of the 3C-SiC/Si-based devices have utilized only the 3C-SiC layer as a functioning layer. This research aims to theoretically and experimentally investigate the optical and optoelectronic e ects on 3C-SiC/Si heterojunctions and explores the potential of enhancing the sensitivity of 3C-SiC/Si-based devices via the optomechanical coupling e ect. The rst purpose of this study is to examine the e ect of optical illumination on the 3C-SiC thin lm and evaluates the possibility to use it as a thermoresistive sensor for monitoring cell temperature during an optical investigation. Furthermore, this research intends to investigate the photoconductive behaviors of the 3C-SiC/Si heterojunction under UV and visible illuminations. The characteristics of the heterojunction are also evaluated under broad spectral illuminations (UV-NIR) to prove its potential to perform as a self-powered photodetector. In addition, the possibility of enhancing the sensitivity of a 3C-SiC/Si heterostructure based piezoresistive sensor by employing the optomechanical coupling e ect is also examined. The results from this study imply the feasibility of using 3C-SiC/Si heterostructure for various M/NEMS applications (such as photodetectors, thermoresistive sensors, and piezoresistive sensors) in optical environments. Moreover, the in-depth discussion about the carrier generation and transport mechanisms will provide vital information for the development of 3C-SiC/Si optoelectronic devices. This thesis is prepared in a \thesis by publications" format. The published journal articles are presented in chapters 3 (partially), 4, 5, and 6.