Polarization control in Nitride Quantum Well Light Emitters Enabled by Bottom Tunnel-junctions

TL;DR

This paper introduces a novel bottom-tunnel junction approach for nitride quantum well light emitters, aligning internal polarization fields to significantly enhance efficiency and enable new device architectures.

Contribution

It presents a new bottom-tunnel junction design that improves polarization alignment, eliminates p-type contacts, and increases light emission efficiency in nitride quantum well LEDs.

Findings

Achieved 200-300% increase in light emission efficiency.

Enabled new geometries for stacking multiple light emitters.

Demonstrated alignment of polarization fields improves carrier recombination control.

Abstract

The frozen internal polarization-induced electric fields due to broken inversion symmetry in all conventional blue and green nitride semiconductor light emitting semiconductor quantum well heterostructures point in a direction opposite to what is desired for efficient flow of electrons and holes. This state of affairs has persisted because of the desire to have p-type hole injectors on top of the quantum well active region. Because of the internal polarization fields in nitride heterostructures, there exist four permutations of doping and polarization for the realization of such light emitters. Which permutation is the most desirable for efficient light emission? In this work, we answer this question by demonstrating a fundamentally new approach towards efficient light emission with bottom-tunnel junctions. The bottom-tunnel junction design aligns the polarization fields in a desired direction in the quantum well, while simultaneously eliminating the need for p-type contacts, and allowing efficient current spreading. By preventing electron overshoot past quantum wells, it disables carrier recombination in undesired regions of the quantized heterostructures, and opens up the possibility for new geometries of integrating and stacking multiple light emitters. Due to the inherent advantages, the bottom-tunnel junction light emitting diode enables a 200-300% increase in the light emission efficiency over alternate heterostructure designs.