Characteristic improvements of thin film AlGaInP red light emitting diodes on a metallic substrate

We report a type of thin film AlGaInP red light emitting diode (RLED) on a metallic substrate by electroplating copper (Cu) to eliminate the absorption of GaAs grown substrate. The fabrication of the thin film RLED is presented in detail. Almost no degradations of epilayers properties are observed after this substrate transferred process. Photoluminescence and electroluminescence are measured to investigate the luminous characteristics. The thin film RLED shows a significant enhancement of light output power (LOP) by improving the injection efficiency and light extraction efficiency compared with the reference RLED on the GaAs parent substrate. The LOPs are specifically enhanced by 73.5% and 142% at typical injections of 2 A/cm² and 35 A/cm² respectively from electroluminescence. Moreover, reduced forward voltages, stable peak wavelengths and full widths at half maximum are obtained with the injected current increasing. These characteristic improvements are due to the Cu substrate with great current spreading and the back reflection by bottom electrodes. The substrate transferred technology based on electroplating provides an optional way to prepare high-performance optoelectronic devices, especially for thin film types. (paper)