Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 61: Semiconductor Surfaces: Adsorption and Reactivity

O 61.2: Vortrag

Mittwoch, 3. April 2019, 15:15–15:30, H25

The impact of Al on defects introduced during GaP nucleation on Si(100) 2° substrate by MOCVD — •Manali Nandy, Agnieszka Paszuk, Christian Koppka, Oliver Supplie, Peter Kleinschmidt, and Thomas Hannappel — Institute for Physics, University of Technology, Ilmenau, Germany

The performance of III-V-on-Si multi-junction solar cells is still limited by a high density of defects at the GaP/Si heterointerface and in the III-V buffer. Here, the GaP buffers are grown on Si(100)2° substrates by metalorganic chemical vapor deposition in Al-free (as a reference) or in Al-containing reactors. In the latter one, Al was supplied either directly during the GaP nucleation from the TMAl precursor or indirectly from Al residuals present in the reactor from previous processes. Defects in the GaP buffers are investigated by electron channeling contrast imaging (ECCI). The GaP buffers grown on GaP nucleation in the Al-free reactor exhibit short misfit dislocations (MDs) and a high density of stacking faults (SFs). In contrast, in the GaP buffers prepared in the Al-containing reactor, the MDs are longer and the density of SFs is lower. Long MDs reduce the lattice strain which results in a smoother GaP surface morphology compared to the GaP buffers with short MDs. GaP buffers grown on modified GaP nucleation layer with Al exhibit even longer MDs, lower density of threading dislocations and very smooth surface morphology. Possibly due to the lower mobility of Al compared to Ga, the surface coverage during the nucleation is improved, which further may affect the crystal quality in the GaP buffer [1].[1] A. C. Lin et al., J. Vac. Sci. Tech. B 29, 3, (2011).