Utilization of native oxygen in Eu(RE)-doped GaN for enabling device compatibility in optoelectronic applications

Abstract

The detrimental influence of oxygen on the performance and reliability of V/III nitride based devices is well known. However, the influence of oxygen on the nature of the incorporation of other co-dopants, such as rare earth ions, has been largely overlooked in GaN. Here, we report the first comprehensive study of the critical role that oxygen has on Eu in GaN, as well as atomic scale observation of diffusion and local concentration of both atoms in the crystal lattice. We find that oxygen plays an integral role in the location, stability, and local defect structure around the Eu ions that were doped into the GaN host. Although the availability of oxygen is essential for these properties, it renders the material incompatible with GaN-based devices. However, the utilization of the normally occurring oxygen in GaN is promoted through structural manipulation, reducing its concentration by 2 orders of magnitude, while maintaining both the material quality and the favorable optical properties of the Eu ions. These findings open the way for full integration of RE dopants for optoelectronic functionalities in the existing GaN platform.

Enhanced photo/electroluminescence properties of Eu-doped GaN through optimization of the growth temperature and Eu related defect environment

“…Moreover, the PL spectra of samples growth with EuCp pm 2 are typically quite broad, unless additional O is co-doped. 13 However, the PL spectra of the samples grown at lower temperatures were more resolved than the samples grown at l030 • C.…”

“…13 Using this source, it was found that either additionally supplied oxygen or a new growth structure was necessary to attain uniform Eu incorporation and luminescence properties comparable to samples grown with the commonly used Eu source, Eu(DPM) 3 . [5][6][7][8][9][10][11][12] Also, when additional oxygen was not supplied, it was found that ∼30% of the Eu ions no longer occupied Ga sites, as is typical in GaN:Eu.…”

“…It was previously reported that for samples grown at 1030 • C with EuCp pm 2 as the Eu precursor, it was necessary to co-dope the sample with additional oxygen in order to reduce surface precipitation and attain more resolved PL spectra. 13 Therefore, it appears that lowering the growth temperature produces a growth environment where more of the oxygen that is normally introduced during the OMVPE growth of all GaN is incorporated. This growth condition also facilitates the formation of new V Ga -O N complexes.…”

“…[5][6][7][8][9][10][11][12] Also, when additional oxygen was not supplied, it was found that ∼30% of the Eu ions no longer occupied Ga sites, as is typical in GaN:Eu. 13,14 Several studies have shown that the defect environment in GaN, such as the vacancy and impurities concentrations, can be modified by controlling growth temperature. [15][16][17] In this article, a new defect environment is achieved by utilizing EuCp pm 2 as the Eu source and adjusting the growth temperature, which led to a significant enhancement in the emission intensity of a GaN:Eu based red LED.…”

Substantial enhancement of red emission intensity by embedding Eu-doped GaN into a microcavity

“…The Eu precousor was bis(n-propyl-tetramethylcyclopentadienyl)europium [(EuCp pm 2 )], and Ar-diluted O 2 was used for oxygen co-doping, which is known to improve the Eu incorporation and luminescence properties, when this Eu source is used. 17 The samples were characterized by photoluminescence (PL) and time-resolved PL (TR-PL). In OMVPE grown GaN:Eu, Eu is known to incorporate into multiple environments, and at least eight distinct optically-active centers have been identified .…”