Estimation of free carrier concentrations in high-quality heavily doped GaN:Si micro-rods by photoluminescence and Raman spectroscopy

M. S. Mohajerani; S. Khachadorian; C. Nenstiel; T. Schimpke; A. Avramescu; M. Strassburg; A. Hoffmann; A. Waag

doi:10.1117/12.2212890

8 March 2016 Estimation of free carrier concentrations in high-quality heavily doped GaN:Si micro-rods by photoluminescence and Raman spectroscopy

M. S. Mohajerani, S. Khachadorian, C. Nenstiel, T. Schimpke, A. Avramescu, M. Strassburg, A. Hoffmann, A. Waag

Author Affiliations +

Proceedings Volume 9768, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XX; 976803 (2016) https://doi.org/10.1117/12.2212890
Event: SPIE OPTO, 2016, San Francisco, California, United States

Abstract

The controlled growth of highly n-doped GaN micro rods is one of the major challenges in the fabrication of recently developed three-dimensional (3D) core-shell light emitting diodes (LEDs). In such structures with a large active area, higher electrical conductivity is needed to achieve higher current density. In this contribution, we introduce high quality heavily-doped GaN:Si micro-rods which are key elements of the newly developed 3D core-shell LEDs. These structures were grown by metal-organic vapor phase epitaxy (MOVPE) using selective area growth (SAG). We employed spatially resolved micro-Raman and micro-photoluminescence (PL) in order to directly determine a free-carrier concentration profile in individual GaN micro-rods. By Raman spectroscopy, we analyze the low-frequency branch of the longitudinal optical (LO)-phonon-plasmon coupled modes and estimate free carrier concentrations from ≈ 2.4 × 10¹⁹ cm−3 up to ≈ 1.5 × 10²⁰ cm^-3. Furthermore, free carrier concentrations are determined by estimating Fermi energy level from the near band edge emission measured by low-temperature PL. The results from both methods reveal a good consistency.

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M. S. Mohajerani, S. Khachadorian, C. Nenstiel, T. Schimpke, A. Avramescu, M. Strassburg, A. Hoffmann, and A. Waag "Estimation of free carrier concentrations in high-quality heavily doped GaN:Si micro-rods by photoluminescence and Raman spectroscopy", Proc. SPIE 9768, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XX, 976803 (8 March 2016); https://doi.org/10.1117/12.2212890

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KEYWORDS

Raman spectroscopy

Gallium nitride

Doping

Light emitting diodes

Luminescence

Crystals

Sapphire

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