Design and Demonstration of Ultra Wide Bandgap AlGaN Tunnel Junctions

TL;DR

This paper presents the design and experimental validation of polarization-engineered ultra-wide bandgap AlGaN tunnel junctions, enabling highly efficient UV LEDs with low resistance and voltage, addressing key limitations in UV LED technology.

Contribution

It introduces a novel polarization engineering approach for AlGaN tunnel junctions, achieving low resistance and enabling efficient UV-C light emission in wide bandgap materials.

Findings

Achieved low tunneling resistance below 10^-3 Ohm cm^2

Demonstrated 292 nm UV emission with non-equilibrium hole injection

Modeling shows potential for low-voltage, high-efficiency UV LEDs

Abstract

Ultra violet light emitting diodes (UV LEDs) face critical limitations in both the injection efficiency and light extraction efficiency due to the resistive and absorbing p-type contact layers. In this work, we investigate the design and application of polarization engineered tunnel junctions for ultra-wide bandgap AlGaN (Al mole fraction higher than 50%) materials towards highly efficient UV LEDs. We demonstrate that polarization-induced 3D charge is beneficial in reducing tunneling barriers especially for high composition AlGaN tunnel junctions. The design of graded tunnel junction structures could lead to low tunneling resistance below 10-3 Ohm cm2 and low voltage consumption below 1 V (at 1 kA/cm2) for high composition AlGaN tunnel junctions. Experimental demonstration of 292 nm emission was achieved through non-equilibrium hole injection into wide bandgap materials with bandgap energy larger than 4.7 eV, and detailed modeling of tunnel junctions shows that they can be engineered to have low resistance, and can enable efficient emitters in the UV-C wavelength range.