Time-resolved electroluminescence studies of Ⅲ-nitride ultraviolet photonic-crystal light-emitting diodes

摘要

Transient responses of Ⅲ-nitride photonic-crystal (PC) ultraviolet (UV) light-emitting diodes (LEDs) were measured by picosecond time-resolved electroluminescence (EL) spectroscopy. Triangular arrays of PCs with different diameters/periodicities were fabricated on 333 nm UV LEDs for enhancing light extraction efficiency using electron-beam lithography and inductively coupled-plasma dry etching. With the incorporation of PCs on LEDs, the EL decay time constant τ decreases systematically with the increase of the etched sidewall area indicating the strong effect of the surface recombination. The surface recombination velocities on the p-type epitaxial surface and on the sidewall of etched holes on LEDs were determined to be 1.73 X 10~4cm/s and 1.48 X 10~5 cm/s, respectively. The angular distribution of light emission from LEDs with PCs shows slight narrowing in far-field pattern. Because of the increased transient response along with enhanced light extraction, the incorporation of PCs in UV LEDs provide an effective method to control the modulation speed of UV LEDs, which could be very useful for many applications.