Investigation of process technologies for the fabrication of AlGaInP mesa ultra high brightness light emitting diode

AlGaInP ultra-high-brightness light emitting diodes (UHB-LED) have gained importance for a variety of applications, such as daylight large area displays. We investigated the influence of the deposition temperature and of the device fabrication process on the performance of orange AlGaInP-DH LEDs grown by MOVPE with standard precursors. The layers were processed into mesa-LEDs and the electrical and optical properties were measured. The highest electroluminescence (EL) and photoluminescence (PL) light intensities were found for TD=750°C and the series resistances exhibit optimal values of RS=9.7 Ω. Semiconductor etching for mesa structures as well as metal etching and different photoresist liftoff techniques for contact patterning are addressed. The process variations are compared with respect to the electrical and optical performance of the devices as well as to their reproducibility and yield. Topics like underetching of the metal multilayers and side reactions between the metal etchants and the photoresist are addressed. The mesa etchant HCl (37%):CH3COOH (99.8%):H2O2 (30%) was investigated over a wide range of compositions and the etch-results were characterized with respect to surface morphology and etch speed. The volume % composition ratio 31:62:7 was found to give a high etch speed of 2.2 μm min−1 through all layers of the structure combined with an excellent surface morphology.