Improving the luminescence of InGaN-GaN blue LEDs through selective ring-region activation of the Mg-doped GaN layer

In this study, we used the selective ring-region activation technique to restrain the surface leakage current and to monitor the luminescence characteristics of InGaN-GaN multiple quantum-well blue light-emitting diodes (LEDs). To access the current blocking region after forming a periphery high-resistance ring-region of the Mg-doped GaN layer and to reduce the degree of carrier trapping by the surface recombination centers, we deposited a titanium film onto the Mg-doped GaN epitaxial layer to form a high-resistance current blocking region. To characterize their luminescence performance, we prepared LEDs incorporating titanium films of various widths of the highly resistive current blocking layer. The hole concentration in the Mg-doped GaN epitaxial layer decreased from 3.45 × 10^-17 cm^-3 to 3.31 × 10¹⁶ cm^-3 after capping with a 250-nm-thick layer of titanium and annealing at 700 °C under a nitrogen atmosphere for 30 min. Furthermore, the luminescence characteristics could be improved by varying the width of the highly resistive region of the current blocking area; in our best result, the relative electroluminescence intensity was 30% (20 mA) and 50% (100 mA) higher than that of the as-grown blue LEDs.