Vertically Conductive Single-Crystal SiC-Based Bragg Reflector Grown on Si Wafer

Optothermotronic effect as an ultrasensitive thermal sensing technology for solid-state electronics

The thermal excitation, regulation, and detection of charge carriers in solid-state electronics have attracted great attention toward high-performance sensing applications but still face major challenges. Manipulating thermal excitation and transport of charge carriers in nanoheterostructures, we report a giant temperature sensing effect in semiconductor nanofilms via optoelectronic coupling, termed optothermotronics. A gradient of charge carriers in the nanofilms under nonuniform light illumination is coupled with an electric tuning current to enhance the performance of the thermal sensing effect. As a proof of concept, we used silicon carbide (SiC) nanofilms that form nanoheterostructures on silicon (Si). The sensing performance based on the thermal excitation of charge carriers in SiC is enhanced by at least 100 times through photon excitation, with a giant temperature coefficient of resistance (TCR) of up to -50%/K. Our findings could be used to substantially enhance the thermal sensing performance of solid-state electronics beyond the present sensing technologies.

3C-SiC/Si Heterostructure: An Excellent Platform for Position-Sensitive Detectors Based on Photovoltaic Effect

Single-crystalline silicon carbide (3C-SiC) on the Si substrate has drawn significant attention in recent years due to its low wafer cost and excellent mechanical, chemical, and optoelectronic properties. However, the applications of the structure have primarily been focused on piezoresistive and pressure sensors, bio-microelectromechanical system, and photonics. Herein, we report another promising application of the heterostructure as a laser spot position-sensitive detector (PSD) based on the lateral photovoltaic effect (LPE) under nonuniform optical illuminations at zero-bias conditions. The LPE shows a linear dependence on spot positions, and the sensitivity is found to be as high as 33 mV/mm under an illumination of 2.8 W/cm² (635 nm). The structure also exhibits a linear dependence of the LPE over a large distance (7 mm) between two electrodes, which is crucial for PSDs as the region with a linear dependence of LPE is only usable for PSDs. The LPE at different spot positions and under different illumination conditions have been investigated and explained based on the energy-band analysis. The temperature dependence of the LPE and position sensitivity is also investigated. Furthermore, the two-dimensional mapping of the lateral photovoltages reveals the potential for utilizing the 3C-SiC/Si heterostructure to detect the laser spot position precisely on a plane.

Excellent Rectifying Properties of the n-3C-SiC/p-Si Heterojunction Subjected to High Temperature Annealing for Electronics, MEMS, and LED Applications

This work examines the stability of epitaxial 3C-SiC/Si heterojunctions subjected to heat treatments between 1000 °C and 1300 °C. Because of the potential for silicon carbide in high temperature and harsh environment applications, and the economic advantages of growing the 3C-SiC polytype on large diameter silicon wafers, its stability after high temperature processing is an important consideration. Yet recently, this has been thrown into question by claims that the heterojunction suffers catastrophic degradation at temperatures above 1000 °C. Here we present results showing that the heterojunction maintains excellent diode characteristics following heat treatment up to 1100 °C and while some changes were observed between 1100 °C and 1300 °C, diodes maintained their rectifying characteristics, enabling compatibility with a large range of device fabrication. The parameters of as-grown diodes were J₀ = 1 × 10⁻¹¹ A/mm², n = 1.02, and +/−2V rectification ratio of 9 × 10⁶. Capacitance and thermal current-voltage analysis was used to characterize the excess current leakage mechanism. The change in diode characteristics depends on diode area, with larger areas (1 mm²) having reduced rectification ratio while smaller areas (0.04 mm²) maintained excellent characteristics of J₀ = 2 × 10⁻¹⁰ A/mm², n = 1.28, and +/−2V ratio of 3 × 10⁶. This points to localized defect regions degrading after heat treatment rather than a fundamental issue of the heterojunction.

Growth mechanism for alternating supply epitaxy: the unique pathway to achieve uniform silicon carbide films on multiple large-diameter silicon substrates

The unique growth mechanism of alternating supply epitaxy enables uniform 3C-SiC to be deposited on multiple large-diameter Si wafers.