High-Responsivity and Fast-Response Ultraviolet Phototransistors Based on Enhanced p-GaN/AlGaN/GaN HEMTs

We report high-performance visible-blind ultraviolet (UV) phototransistors (PTs) based on an enhanced HEMT structure. In dark conditions, the conduction channel was depleted, and the dark current density was suppressed to 2.63 × 10–10 mA/mm. Under 345 nm UV illumination, the depletion region shrinks, and the two-dimensional electron gas (2DEG) recovers. A high photocurrent density of 37.39 mA/mm, a peak responsivity of 6.80 × 104 A/W, a large photo-to-dark-current ratio (PDCR) of 1.42 × 1011, and a superior UV-to-visible rejection ratio (UVRR) of 4.84 × 107 are exhibited. Most importantly, the device presents an ultrafast response time of 11.33 μs/65.52 μs, which is due to the significant suppression of the persistent photoconductivity effect by the built-in electric field in the p–n junction. The results suggest that the p-GaN/AlGaN/GaN PT is a brand-new device model that combines the advantages of photoconductors with high responsivity and photodiodes with low dark current and fast response time.