研究目的
Investigating the performance and operating principle of a 4H-SiC UV phototransistor with high optical gain and sensitivity to ultraviolet radiations.
研究成果
The fabricated 4H-SiC UV phototransistors demonstrate significant improvements in optical gain, sensitivity, and rejection of visible radiations compared to the state-of-the-art. The operating principle, based on the variation in the potential barrier height due to photogenerated electron-hole pairs, has been experimentally proved. The device's structure allows for easy integration and potential performance improvements with additional layers like antireflecting coatings.
研究不足
The study does not include dynamic analysis, such as transient response, which is required to fully understand the device's performances and compare it with electro-optical devices based on other semiconductor technologies.
1：Experimental Design and Method Selection:
The study involves the fabrication and characterization of a 4H-SiC UV phototransistor designed to detect UV radiations with wavelengths lower than 380 nm. The device's structure is optimized to have the electric field extend up to the radiated surface for efficient separation of photogenerated electron-hole pairs.
2：Sample Selection and Data Sources:
The devices were fabricated starting from a 4H-SiC 100-mm 20-mΩ·cm n-type wafer, followed by epitaxial growth and various processing steps including ion implantation, thermal annealing, and deposition of metal layers.
3：List of Experimental Equipment and Materials:
HP 4155B semiconductor parameter analyzer for electrical and optical characterizations, LOT-Quantum Design MSH-150 monochromatic optical system with a 50-W Xe arc lamp for UV light selection, THORLABS optical power and energy meter PM100D and S120VC photodiode power sensor for optical power density measurements.
4：Experimental Procedures and Operational Workflow:
The phototransistor operation was defined with a floating gate configuration, where the gate contact is floating, the source is grounded, and the drain is biased by an external voltage source. Electrical characterizations under dark condition and optical characterizations under UV radiation were performed.
5：Data Analysis Methods:
The responsivity and optical gain were extracted from the photocurrent and optical power density measurements. The dynamic range was calculated to evaluate the device's performance.
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