Raman Imaging Properties and Phonon Dynamics Analysis of GaInN/GaN Heterostructures using a Double Laser System

Heat energy transport is reportedly significantly blocked at the heterointerfaces in semiconductors. However, imaging the transport across heterointerfaces remains challenging. This article presents the advantages of an imaging system using two lasers for heating and probing. Samples with heterostructures of Ga_1−xIn_xN (0.1‐μm thick, x: 0.05–0.17)/GaN (3.0–6.5‐μm thick) on α‐Al₂O₃ substrates are examined using a 532‐nm laser to probe the temperature increase in the GaN underlayer and a 325‐nm laser to heat and probe the GaInN layer. The results show that the phonon diffusion length in Ga_1−xIn_xN is a few micrometers and is lower for higher InN mole fraction x. A significant block of the phonon transport at the heterointerface is observed. The interfacial transport is primarily governed by the alignment of the E₂(high) mode energy between the two layers forming the interface. This condition arises from the nature of the E₂(high) mode, which acts as an intermediate mode in the decomposition process of immobile longitudinal optical mode to mobile acoustic modes. Moreover, this experimental setup can be used to investigate phonon transport across multiple quantum well structures.