Characterization of non-uniform InGaN alloys: spatial localization of carriers and optical properties

A. Di Vito,A. Di Carlo,M. Auf der Maur,A. Pecchia

doi:10.7567/1347-4065/ab06ba

A. Di Vito, A. Di Carlo + Show 2 more

Open Access

https://doi.org/10.7567/1347-4065/ab06ba

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Abstract

Statistical indium fluctuations in InGaN alloys have been demonstrated to induce spatial localization of carriers. This phenomenon has a strong influence on the behavior of InGaN based light emitting diodes and it is further exacerbated by the presence of compositional non-uniformities. In the present work, we theoretically characterize non-uniform InGaN alloys, taking into account the impact of indium clustering on the electronic and optical properties of the material. The assumption of a non-uniform indium distribution within the bulk structure results in a reduction of the band gap energy and a broadening of the absorption edge with respect to the uniform random alloy configuration, in agreement with the experimental results found in literature. Moreover, we find that it is crucial to consider the presence of compositional non-uniformity in order to derive a theoretical description that is consistent with the outcomes of the experimental studies, especially when the indium content exceeds 10%. Such an effect suggests that a growing indium concentration yields an increment in the amount of indium clustering. Finally, we use the Getis–Ord statistics in order to derive the characteristic localization length of the carriers. This is an original application of this method, usually employed in geospatial analysis.

Highlights

Indium Gallium Nitride (InGaN) alloys have gained increasing attention in the last decades due to their successful application in optoelectronic devices
We show that the ground state hole wave function is localized within indium rich regions. Such an effect is exacerbated by the presence of indium clusters, as we demonstrate in Sect. 3.2, where we use the Getis–Ord statistics in order to quantify the degree of compositional non-uniformity and derive the characteristic localization length of the carriers
We show that the presence of indium clusters induces a reduction of the band gap energy with respect to the uniform alloy and a broadening of the absorption edge, in agreement with the experimental results found in literature. 3.1

Summary

Introduction

Indium Gallium Nitride (InGaN) alloys have gained increasing attention in the last decades due to their successful application in optoelectronic devices. The role of compositional non-uniformity in the spatial localization of carriers and its impact on the performance of InGaN devices has not been extensively discussed. The influence of compositional non-uniformity on the carrier localization is considered, where we use the Getis–Ord statistics16) to detect the presence of indium clusters within the structure and derive the degree of localization and the characteristic localization length of the carriers. This is the first application of the Getis–Ord statistics in the field of condensed matter physics. We find that the non-uniformity induces a broadening of the absorption edge, as pointed out in recent experimental results.17) our analysis suggests that the non-uniformity is more pronounced when the mean indium content increases

Theoretical approach

Results and discussion

Conclusions