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HL: Fachverband Halbleiterphysik

HL 24: Thermal Properties

HL 24.1: Vortrag

Dienstag, 18. März 2025, 12:15–12:30, H14

Combined optical and thermal characterization of III-nitride membranes by microphotoluminescence and Raman thermometry — •Gordon Callsen¹, Mahmoud Elhajhasan¹, Julian Themann¹, Katharina Dudde¹, Guillaume Würsch¹, Jean-François Carlin², Raphaël Butté², Nicolas Grandjean², Nakib Haider Protik³, and Giuseppe Romano⁴ — ¹Universität Bremen, Germany — ²EPFL, Lausanne, Switzerland — ³HU Berlin, Germany — ⁴MIT-IBM Watson AI Lab, Cambridge, USA

We present the optical and thermal analysis of photonic III-nitride membranes, which provides novel insights into the physics of thermal transport on the micrometer scale [1]. By combining Raman thermometry (RT) with µPL spectroscopy, we demonstrate a non-invasive approach to extract the thermal conductivity κ. This analysis shows that even at 295 K one can still observe quasi-ballistic phonon transport in GaN, which challenges commonly applied models building on purely diffusive transport. Our membranes are made from c-plane GaN and comprise In_xGa_1−xN (e.g., x = 0.15) quantum wells that already served as an active medium in various nanolasers [2]. The material is either grown on silicon or sapphire and is subsequently underetched, yielding freestanding structures. On such samples we perform µ-RT, either based on one-laser RT or spatially resolved two-laser RT. The latter is key to our thermal imaging, representing a significant step towards non-invasive and quantitative thermometry on photonic membranes. [1] M. Elhajhasan et al., PRB 108, 235313 (2023) [2] S. T. Jagsch et al., Nat. Commun. 9, 564 (2018)

Keywords: thermal conductivity; thermal imaging; photoluminescence; Raman; nitrides