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Carrier localization structure combined with current micropaths in AlGaN quantum wells grown on an AlN template with macrosteps

Authors :
Masamichi Ippommatsu
Yosuke Nagasawa
Hiroshi Amano
Isamu Akasaki
Akira Hirano
Shigefusa F. Chichibu
Kazunobu Kojima
Yoshio Honda
Source :
Applied Physics Letters. 114:011102
Publication Year :
2019
Publisher :
AIP Publishing, 2019.

Abstract

The microscopic structural and optical characteristics of AlGaN-based light-emitting diodes grown on AlN templates with macrosteps were evaluated. Cross-sectional transmission electron microscopy in the high-angle annular dark field scanning mode and microscopic energy dispersive X-ray spectroscopy reveal that the AlGaN cladding layer under the AlGaN quantum wells (QWs) has microscopic compositional modulations originating from the macrosteps at the AlN template surface. The Ga-rich oblique zones in the cladding layer likely behave as current micropaths. These micropaths are connected to the carrier localization structure, which is formed by the modulation of both the well widths and the compositions of the QWs. In-plane spatially-resolved cathodoluminescence (CL) spectroscopy indicated significant inhomogeneity of the CL characteristics: the brighter emission with a lower peak photon energy confirms the existence of the carrier localization structure in the QWs. Carrier localization in the QWs along with the current micropaths in the AlGaN cladding layer appears to increase the external quantum efficiency of AlGaN LEDs.

Details

ISSN :
10773118 and 00036951
Volume :
114
Database :
OpenAIRE
Journal :
Applied Physics Letters
Accession number :
edsair.doi...........eb3c451bb5734e848396ba890638f8b3