Site-selective enhancement of Eu emission in delta-doped GaN

TL;DR

This study demonstrates that delta-doping of Eu in GaN selectively enhances emission from the majority site, leading to more efficient and homogeneous photoluminescence suitable for LEDs and quantum applications.

Contribution

The paper introduces a delta-doping technique to control Eu site occupancy in GaN, improving emission efficiency and spectral homogeneity over traditional uniform doping methods.

Findings

Delta-doped GaN:Eu shows increased PL intensity per Eu concentration.

Energy transfer efficiency to the majority site is improved with delta-doping.

1-nm delta-doped layers produce homogeneous emission from the majority site.

Abstract

Europium-doped gallium nitride (GaN:Eu) is a promising platform for classical and quantum optoelectronic applications. When grown using organometallic vapor-phase epitaxy, the dominant red emission from Eu exhibits an inhomogeneous photoluminescence (PL) spectrum due to contributions from several non-equivalent incorporation sites that can be distinguished with combined excitation emission spectroscopy. Energy transfer from the GaN bandgap to the majority site is inefficient, limiting the performance of GaN:Eu LEDs and resulting in an inhomogeneous emission spectrum dominated by disproportionate contributions from minority sites. In this work, we use site-selective spectroscopy to characterize the photoluminescence properties of delta-doped structures with alternating doped and undoped layers of varying thicknesses and demonstrate that they selectively enhance emission from the majority site when compared to uniformly-doped samples. Samples with 2-nm and 10-nm doped layers show much greater PL intensity per Eu concentration as well as more efficient energy transfer to the majority site, which are both highly desirable for creating power-efficient LEDs. Meanwhile, a sample with 1-nm doped layers shows emission only from the majority site, resulting in a narrow, homogeneous emission spectrum that is desirable for quantum technologies. This utilization of delta-doping has the potential to be broadly applicable for engineering desirable defect properties in rare-earth doped semiconductors.