| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Thin Films | Tuesday Sessions |
| Session TF-TuM |
| Session: | Nanostructured Surfaces & Thin Films II |
| Presenter: | Manolo Ramírez López, Instituto Politécnico Nacional, Mexico |
| Authors: | M. Ramírez López, Instituto Politécnico Nacional, Mexico L. Janicki, Institute of Physics, Wroclaw University of Technology, Poland R. Kudrawiec, Institute of Physics, Wroclaw University of Technology, Poland M. Baranowski, Institute of Physics, Wroclaw University of Technology, Poland J. Misiewicz, Institute of Physics, Wroclaw University of Technology, Poland M. Zhao, IMEC, Belgium K. Kai Cheng, IMEC, Belgium |
| Correspondent: | Click to Email |
Intensive efforts have been made to improve electrical performance of GaN-based HEMT transistors but it has not been identified factors that limit the breakdown voltage, electrical mobility and lead to the early device failure[1]. Incorporation of impurities, point defects, dislocations and grain boundaries formed at semiconductor layers of the device are good candidates to explain their electrical limitations. This work was focused to study the effect of non-intentional carbon concentration on optical recombination processes in AlGaN buffer layer and GaN channel of HEMT transistors grown by MOCVD technique. Samples were grown by changing growth temperature from 950 to 1040 oC, which reduced carbon concentration from 8x1019 to 5x1017 atoms/cm3 (measured by SIMS). Low temperature photoluminescence (PL) spectra of AlGaN buffer layers where show yellow band(YL), blue band(BL) and near band emissions (NBE), whose relative intensities are well related with dislocation density and carbon incorporation. Optical quenching phenomena on YL, BL and NBE was observed as temperature increases and NBE peak position suffers a redshift as carbon concentration decreases [2]. In samples with high carbon concentration (8x1019 and 2x1019 atoms/cm3) only carrier redistribution within localized state was observed, while for samples with lowest carbon concentration (5x1017 to 3x1018 atoms/cm3) two optical quenching process were identified (carrier redistribution and delocalization). Carrier delocalization was confirmed by yellow-band intensity increase when this process was thermally activated at 150 K. Results are explained in terms of carbon-generated localized states with different depth and aluminum fluctuations within AlGaN buffer layers. High-resolution PL spectra of C-doped layers show free A exciton and acceptor bound-exciton whose intensities are correlated with crystal quality and carbon concentration. Complementary analysis will be presented for GaN channel of HEMT transistors.
[1] E. Zanoni, M. Meghini, A. Chini, D. Marcon and G. Meneghesso, IEEE Transactions On Electron Devices, 60, 10 (2013).
[2] M. A. Reshchikov, D. O. Demchenko, A. Usikov, H. Helava, and Yu. Makarov, Phys. Rev. B 90, 235203 (2014).
This work was performed within the grant of the National Science Center (NCS) (OPUS 5 No. 2013/09/B/st7/02395), and supported by SIP-IPN project No. 20160610. The authors acknowledge to CONACYT for financial support though postdoctoral scholarship No. 265970.