A Low-Temperature External Electron Retarding Electrode for Improving Vertical Green LED Performance

Abstract

To alleviate the mismatch between electron/hole velocities and improve the quantum efficiencies, the cobalt-doped ZnO (CZO) dilute magnetic films grown by pulsed-laser deposition at a low temperature of 100 °C were served as the external electron retarding n-electrodes for vertical InGaN light-emitting diodes (LEDs). The retardation of the electron mobility is owing to the scatter of electrons via the spin-orbit interaction of Co2+ ions and their corresponding ferromagnetic properties. A 150-nm-thick CZO film was chosen as the n-electrode for the vertical green LED (530 nm). In comparison to conventional lateral LED, the vertical LEDs without and with the CZO n-electrode had 21.3% and 39.6% improvements in the output power (at 350 mA), respectively. The vertical LED with the CZO n-electrode showed an increment in the light output power (at 350 mA) by 15.1% as compared with the vertical LED without the CZO n-electrode. Obviously, after inserting the CZO n-electrode, the excessively large mobility difference between the electron and hole carriers in the conventional vertical LED is reduced significantly, which can decrease the nonradiative recombination rate and improve the emission characteristic. The results also reveal the CZO film served as an external electron retarding electrode is highly potential for vertical LED applications.