Reach-Through-Collector Based 4H-SiC Phototransistor Enabling nW/cm2 UV Detection

SiC phototransistor has been widely studied for the weak UV detection, however, is facing with severe limit for the detection of UV light below <inline-formula> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula>/cm2. In this work, reach-through-collector configuration based SiC phototransistor has been demonstrated, where sensitivity of base region to the bias voltage has been largely alleviated, achieving fine control on the neutral zone in the base layer. The tunable gain range for the weak UV light has been extended to over <inline-formula> <tex-math notation="LaTeX">$10^{{8}}$ </tex-math></inline-formula>, while the dark current is kept below 0.5 pA, and the noise figure is as low as <inline-formula> <tex-math notation="LaTeX">$10^{-{28}}\,\,\text{A}^{{2}}$ </tex-math></inline-formula>/Hz at 10 Hz. These characteristics contribute to a UV-to-visible rejection ratio of <inline-formula> <tex-math notation="LaTeX">${1}.{9}\times {10} ^{{7}}$ </tex-math></inline-formula> and a detectivity of <inline-formula> <tex-math notation="LaTeX">${4}.{9}\times {10} ^{{15}}$ </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula>Hz<inline-formula> <tex-math notation="LaTeX">$^{\text {1/{2}}}$ </tex-math></inline-formula>/W, enabling a UV detection with power as low as 5 nW/cm2. With additional advantageous dynamic response performance, this reach-through collector based PTD solution paves a way to SiC based ultra-weak UV detection technology.