Low resistive GaN-based tunnel junctions grown at low temperatures in triple-junction LEDs

We systematically investigated growth temperature dependence on operating voltages of GaN-based tunnel junctions by metalorganic vapor phase epitaxy. Low resistive GaN-based tunnel junctions showing resistivity values approximately 2 × 10−4 Ω cm2 were demonstrated by using considerably low growth temperatures, such as 500 °C for the heavily Mg-doped GaN and 625 °C for the heavily Mg-doped GaInN with a small InN mole fraction ranging from 0.08 to 0.11. These results imply that the tunneling mechanism could not be a simple band-to-band tunneling but the defect level-assisted tunneling. Furthermore, a triple-junction blue-purple light-emitting diode (LED) incorporating the optimized GaInN tunnel junctions exhibited approximately three times higher light output power than that of a single-junction LED, indicating that the GaInN tunnel junctions developed in this study are suitable for nitride-based tandem optoelectronic devices.