Electroluminescence and photocurrent generation in pn-diode of trilayer phosphorene

Van der Waals (vdW) two-dimensional semiconductors exhibit excellent optical properties due to their atomically thin thickness and unique band structures. When they are utilized in optoelectronic device applications, the devices show excellent performance as shown for transition metal dichalcogenides and graphene. However, at telecom frequencies, these demonstrations have been largely missing yet. In this study, we demonstrate that trilayer phosphorene pn-diodes can efficiently emit electroluminescence and generate photocurrent at telecom frequencies. Split gates realize electrically tunable pn-diode devices. Under reverse bias, the device shows prominent photocurrent in the photovoltaic mode. Under forward bias, the device shows prominent electroluminescence at the band edge of 0.82 eV. Interestingly, electroluminescence exhibits strong optical anisotropy due to the crystal anisotropy. Our study shows promising potential of trilayer phosphorene for efficient light emitting and photodetection device applications at telecom frequencies.