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HL: Fachverband Halbleiterphysik

HL 58: Nitrides: Preparation and Characterization II

HL 58.2: Vortrag

Freitag, 21. März 2025, 09:45–10:00, H14

Characterization of structural and optical properties of a red InGaN/GaN MQW LED — •Niklas Dreyer¹, F. Bertram¹, G. Schmidt¹, H. Eisele¹, S. Petzold¹, O. August¹, A. Dempewolf¹, K. Wein¹, J. Christen¹, B. Sheng², and X. Wang² — ¹Otto-von-Guericke-Universität Magdeburg, 39106 Magdeburg, Germany — ²Peking University, Beijing 100871, China

An InGaN/GaN LED with an intended red emission (> 600 nm) was grown by MOVPE on a sapphire substrate. On an undoped GaN buffer followed by a doped n-GaN layer, the active region consists of a stack of three identical sequences, each with three quantum wells (QWs). The first two QWs nominally contain 15 % In (blue) and the third 40 % In (red). Each sequence is confined by an Al_0.32Ga_0.68N layer. Finally, a p-doped Al_0.17Ga_0.83N EBL is positioned, which is further capped by a dielectric DBR and processed, including metal contacts.

The LED is comprehensively characterized by cross-sectional cathodoluminescence performed in scanning transmission electron microscopy (STEM-CL) and by electroluminescence (EL). The luminescence along the growth direction is directly visualized in CL linescans: in particular, each QW can be spectrally and spatially resolved and shows a distinct emission. A wavelength shift for all QWs is observed. Furthermore, the n-GaN exhibits near-band-edge (NBE) luminescence at 356.7 nm at T=16 K corresponding with a high free carrier concentration due to Burstein-Moss Shift.

The EL spectrum shows intense, broad emission around 650 nm, with a weak shift to shorter wavelengths for higher injection current.

Keywords: cathodoluminescence; quantum well; red LED; scanning transmission electron microscopy; InGaN