Low Resistive and Low Absorptive Nitride-Based Tunnel junctions

ABSTRACTWe have investigated two approaches for an alternative hole injection with a tunnel junction targeting deep UV-LEDs. One was an AlGaN-based tunnel junction. We fabricated the AlGaN-based tunnel junctions with various AlN mole fractions (0～0.2) grown on conventional blue-LEDs by MOVPE. A 7.5 nm heavily Mg-doped GaN/15 nm heavily Si-doped Al0.2Ga0.8N tunnel junction showed a large voltage drop, 5.31 V at 20 mA, under reverse bias. The other was a GaInN-based tunnel junction. We prepared Ga0.6In0.4N tunnel junctions with various thicknesses and Si doping levels grown on the blue LEDs by MOVPE. A 2 nm heavily Mg-doped Ga0.6In0.4N/3 nm heavily Si-doped GaN tunnel junction showed only 0.12 V drop at 20mA under reverse bias. Since an absorption of the thin GaInN tunnel junction was estimated to be less than 10 %, such a tunnel junction with small bandgap and thin layer thickness is a practical approach to obtain a low resistive and low absorptive hole injection in the deep UV-LEDs.