Low-Voltage and High-Gain Ultraviolet Detector Based on 4H-SiC n-p-n Bipolar Phototransistor

A two-terminal 4H-SiC n-p-n bipolar phototransistor detector (PTD) with high gain is demonstrated. It was fabricated using the 4H-SiC epitaxial wafer grown by high-temperature chemical vapor deposition. The PTD shows a large photocurrent and responsivity enhancement over the conventional 4H-SiC p-i-n photodetector (PD). These enhancement effects are owing to the internal gain of the bipolar transistor. The detector shows a high optical gain of ~ 1450 at 360 nm and has a linear response to the ultraviolet (UV) light in the wide light intensity range of 0.7– $700~\boldsymbol \mu \text{W}\boldsymbol /$ cm2 at a low operating voltage of 3 V. The PTD can respond to the UV light from 220 to 340 nm and the peak responsivity is $\sim 125~\text{A}\boldsymbol /\text{W}$ at 275 nm. This work is significant for developing high-performance SiC-based bipolar phototransistors.