Indium surfactant assisted epitaxy of non-polar ( 10 1 ¯ 0 ) AlGaN/InGaN multiple quantum well heterostructures

• Published in: Journal of applied physics 2020-09, Vol.128 (11)
• Main Authors: Dzuba, Brandon, Senichev, Alexander, Nguyen, Trang, Cao, Yang, Diaz, Rosa E., Manfra, Michael J., Malis, Oana
• Format: Article
• Language: English
• Subjects: Aluminum base alloys; Aluminum gallium nitrides; Applied physics; Electron states; Epitaxial growth; Flat surfaces; Heterostructures; Indium; Indium gallium nitrides; Inhomogeneity; Low temperature; Molecular beam epitaxy; Morphology; Photoluminescence; Quantum wells; Surfactants
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/5.0020263

The use of an indium surfactant considerably alters the composition and morphology of low-temperature non-polar m-plane ( 10 1 ¯ 0 ) AlxGa1−xN (x ∼ 0.2) and of silicon-doped AlGaN/InGaN multiple quantum wells grown by plasma-assisted molecular beam epitaxy. This paper compares heterostructures grown with indium surfactant with those grown under conventional stoichiometric and gallium-rich conditions at the relatively low temperature necessary for growth of In0.16Ga0.84N quantum wells (565 °C). Stoichiometric growth results in rough, inhomogeneous AlGaN layers that are unsuitable for optical devices. Gallium-rich growth produces a smoother AlGaN layer, reduced inhomogeneities, and sharper interfaces as compared to stoichiometric growth. However, due to the low temperature, gallium-rich growth leads to the formation of an unintentional GaN layer on top of each AlGaN barrier, reducing the energies of confined electronic states in the quantum wells. An indium surfactant enables two-dimensional AlGaN growth at low temperature, producing atomically flat surface morphology and sharp heterostructure interfaces. Indium surfactant assisted epitaxy also eliminates the high aluminum alloy inhomogeneities observed with conventional stoichiometric and gallium-rich growth. Even though partial indium incorporation into the AlGaN layer is found at the studied temperatures, the high-quality, uniform non-polar In0.055Al0.19Ga0.755N/In0.16Ga0.84N quantum wells grown with indium surfactant display bright and narrow photoluminescence that is essential for device applications.