We discover hidden Rashba fine structure in CH3NH3PbI3 and demonstrate its quantum control by vibrational coherence through symmetry-selective vibronic (electron-phonon) coupling. Above a critical threshold of a single-cycle terahertz pump field, a Raman phonon mode distinctly modulates the middle excitonic states with persistent coherence for more than ten times longer than the ones on two sides that predominately couple to infrared phonons. These vibronic quantum beats, together with first-principles modeling of phonon periodically modulated Rashba parameters, identify a threefold excitonic fine structure splitting, i.e., optically forbidden, degenerate dark states in between two bright ones with a narrow, similar to 3 nm splitting. Harnessing of vibronic quantum coherence and symmetry inspires lightperovskite quantum control and sub-THz-cycle "Rashba engineering" of spin-split bands for ultimate multifunction device.

In this paper, self-powered ultraviolet (UV) photodetectors with high response performance based on Ga 2 O 3 /p-GaN were fabricated by metal−organic chemical vapor deposition (MOCVD). The effects of different crystal phases of Ga 2 O 3 (including a, ε, ε/β, and β) grown on p-GaN films on the performance of photodetectors were systematically studied. Moreover, an in situ GaON dielectric layer improved the responsivity of Ga 2 O 3 /p-GaN photodetectors by 20 times. All Ga 2 O 3 /p-GaN photodetectors showed self-power capability without bias. An ultralow dark current of 3.08 pA and a I photo /I dark ratio of 4.1 × 10 3 (1.8 × 10 3 ) under 254 nm (365 nm) light were obtained for the β-Ga 2 O 3 /p-GaN photodetector at 0 V bias. Furthermore, the β-Ga 2 O 3 /p-GaN photodetector showed excellent sensitivity with a high responsivity of 3.8 A/W (0.83 A/W), a fast response speed of 66/36 ms (36/73 ms), and a high detectivity of 1.12 × 10 14 Jones (2.44 × 10 13 Jones) under 254 nm (365 nm) light at 0 V bias. The carrier transport mechanism of the Ga 2 O 3 /p-GaN self-powered photodetector was also analyzed through the device energy band diagram. This work provides critical information for the design and fabrication of high-performance self-powered Ga 2 O 3 /p-GaN UV photodetectors, opening the door to a variety of photonic systems and applications without an external power supply.

Paper published as part of the special topic on Lead Halide PerovskitesLHP2019 ARTICLES YOU MAY BE INTERESTED IN Coherent charge-phonon correlations and exciton dynamics in orthorhombic CH 3 NH 3 PbI 3 measured by ultrafast multi-THz spectroscopy