Characteristics of light-emitting diodes based on GaN p-n junctions grown by plasma-assisted molecular beam epitaxy

Abstract

We report on the fabrication and physics of mesa-etched light-emitting diodes (LEDs) made from GaN p-n junctions grown by molecular beam epitaxy. Rapid thermal annealing was found to improve the electrical properties of these LEDs. Annealed LEDs turn on at 4 V, exhibit an on-series resistance of approximately 14 Ω, and have only 36 μA of leakage current for reverse bias levels as high as 10 V. Electroluminescence (EL) spectra obtained from devices driven to 15 mA are dominated by a peak at 400 nm, which is attributed to recombination between shallow donors and Mg luminescent centers on the p side of the junction. The full width at half maximum of this peak is only 30 nm, which, to the best of our knowledge, is the narrowest EL peak measured from a GaN p-n junction LED. In other devices, recombination was found to proceed through defect states in the middle of the band gap. The broad emission from these LEDs can be shifted from the orange to the violet spectral region by adjusting the drive current. In addition, these LEDs withstand dc current densities in excess of 700 A/cm2 at room temperature.