Kinetic energy dependence of carrier diffusion in a GaAs epilayer studied by wavelength selective PL imaging

• Published in: Journal of luminescence Vol. 185; no. C; pp. 200 - 204
• Main Authors: Zhang, S., Su, L.Q., Kon, J., Gfroerer, T., Wanlass, M.W., Zhang, Y.
• Format: Journal Article
• Language: English
• Published: United States Elsevier B.V 01.05.2017; Elsevier
• Subjects: CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Diffusion length; Electron diffusion; GaAs thin film; Photoluminescence imaging; Thermal distribution; Thermal distribution; Photoluminescence imaging; Electron diffusion; Diffusion length; GaAs thin film
• ISSN: 0022-2313; 1872-7883
• DOI: 10.1016/j.jlumin.2017.01.013

Photoluminescence (PL) imaging has been shown to be an efficient technique for investigating carrier diffusion in semiconductors. In the past, the measurement was typically carried out by measuring at one wavelength (e.g., at the band gap) or simply the whole emission band. At room temperature in a semiconductor like GaAs, the band-to-band PL emission may occur in a spectral range over 200meV, vastly exceeding the average thermal energy of about 26meV. To investigate the potential dependence of the carrier diffusion on the carrier kinetic energy, we performed wavelength selective PL imaging on a GaAs double hetero-structure in a spectral range from about 70meV above to 50meV below the bandgap, extracting the carrier diffusion lengths at different PL wavelengths by fitting the imaging data to a theoretical model. The results clearly show that the locally generated carriers of different kinetic energies mostly diffuse together, maintaining the same thermal distribution throughout the diffusion process. Potential effects related to carrier density, self-absorption, lateral wave-guiding, and local heating are also discussed.