Effect of thermal annealing induced by p-type layer growth on blue and green LED performance

We investigated the electrical and structural qualities of Mg-doped p-type In0.01Ga0.99N and GaN layers grown under different growth conditions by metalorganic chemical vapor deposition. It was found that we obtained a lower hole concentration and rough surface by reducing the growth temperature down to 930 °C in the case of p-GaN. A slight improvement of the hole concentration was obtained for Mg-doped In0.01Ga0.99N grown at 840 °C, but this was accompanied by pit formation on the surface. In0.19Ga0.81N/GaN and In0.25Ga0.75N/GaN multiple-quantum-well (MQW) light-emitting diodes (LED) with such different p-layers were also grown. It was found from photoluminescence studies that the optical and structural properties of the MQW in the LED structure were improved by reducing the growth temperature of the p-layer due to reduced thermal annealing effect of the active region during p-layer growth. However, it was also found the electroluminescence intensity was lower for the LEDs with p-In0.01Ga0.99N layers grown at 840 °C.