Self-formed compositional superlattices triggered by cation orderings in m-plane Al1-xInxN on GaN

Shigefusa F Chichibu; Kohei Shima; Kazunobu Kojima; Yoshihiro Kangawa

doi:10.1038/s41598-020-75380-3

Self-formed compositional superlattices triggered by cation orderings in m-plane Al_1-xIn_xN on GaN

Sci Rep. 2020 Oct 29;10(1):18570. doi: 10.1038/s41598-020-75380-3.

Authors

Shigefusa F Chichibu¹, Kohei Shima², Kazunobu Kojima², Yoshihiro Kangawa³

Affiliations

¹ Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba, Sendai, 980-8577, Japan. chichibulab@yahoo.co.jp.
² Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba, Sendai, 980-8577, Japan.
³ Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka, 816-8580, Japan.

Abstract

Immiscible semiconductors are of premier importance since the source of lighting has been replaced by white light-emitting-diodes (LEDs) composed of thermodynamically immiscible In_xGa_1-xN blue LEDs and yellow phosphors. For realizing versatile deep-ultraviolet to near-infrared light-emitters, Al_1-xIn_xN alloys are one of the desirable candidates. Here we exemplify the appearance and self-formation sequence of compositional superlattices in compressively strained m-plane Al_1-xIn_xN films. On each terrace of atomically-flat m-plane GaN, In- and Al-species diffuse toward a monolayer (ML) step edge, and the first and second uppermost < [Formula: see text]> cation-rows are preferentially occupied by Al and In atoms, respectively, because the configuration of one In-N and two Al-N bonds is more stable than that of one Al-N and two In-N bonds. Subsequent coverage by next < [Formula: see text]> Al-row buries the < [Formula: see text]> In-row, producing nearly Al_0.5In_0.5N cation-stripe ordering along [0001]-axis on GaN. At the second Al_0.72In_0.28N layer, this ordinality suddenly lessens but In-rich and In-poor < [Formula: see text]>-rows are alternately formed, which grow into respective {0001}-planes. Simultaneously, approximately 5-nm-period Al_0.70In_0.30N/Al_0.74In_0.26N ordering is formed to mitigate the lattice mismatch along [0001], which grow into approximately 5-nm-period Al_0.70In_0.30N/Al_0.74In_0.26N {[Formula: see text]} superlattices as step-flow growth progresses. Spatially resolved cathodoluminescence spectra identify the emissions from particular structures.

Abstract

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