Regensburg 2025 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 58: Nitrides: Preparation and Characterization II

HL 58.3: Talk

Friday, March 21, 2025, 10:00–10:15, H14

Advanced nano-characterization of doped and undoped InGaN/GaN MQW-LED structures — •Luca Greczmiel, F. Bertram, G. Schmidt, P. Veit, H. Eisele, A. Dempewolf, S. Petzold, J. Christen, C. Berger, A. Dadgar, and A. Strittmatter — Otto-von-Guericke-Universität Magdeburg, 39106 Magdeburg, Germany

In this study, we comprehensively investigate structural and optical properties of InGaN/GaN MQW-LED-structures by cathodoluminescence (CL) directly performed in a scanning transmission electron microscope (STEM). The LEDs are grown by MOVPE on top of an optimized GaN/sapphire template. The first pn-junction is formed by an 1.6 µ m thick GaN:Si layer and a 345 nm thick GaN:Mg layer, which are nominally doped with a concentration of 7*10¹⁸ cm⁻³ and 2*10¹⁹ cm⁻³, respectively. In between the n- and p-layer a MQW is located, which is composed of a stack of five InGaN QWs being separated by GaN:Si barriers, with a thickness of 3 nm and 7 nm, respectively. The InGaN wells have a nominal In content of 12 %. In STEM-linescans of the active region along the sample cross-section, the first QW shows emission at shorter wavelengths with respect to the subsequent following QWs. For comparison, a second MQW structure was investigated, which was identically grown, but sandwiched between uGaN. In contrast to the first sample, the CL of the 1st QW shifts to longer wavelengths, with respect to the subsequently following QWs. Hence, this spectral shift of the 1st QW is supposed to depend on the electric field in the space charge region.

Keywords: multiple quantum well; cathodoluminescence; scanning transmission electron microscope; InGaN; LED