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O: Fachverband Oberflächenphysik

O 91: Poster Session - Semiconductor Substrates: Structure, Epitaxy and Growth

O 91.3: Poster

Mittwoch, 18. März 2020, 18:15–20:00, P2/1OG

Impact of Al on defect formation in GaP buffer layers grown on Si(100) substrates in CVD ambience — •Manali Nandy¹, Agnieszka Paszuk¹, Christian Koppka¹, Markus Feifel², Peter Kleinschmidt¹, Frank Dimroth², and Thomas Hannappel¹ — ¹Institute of Physics, TU Ilmenau, Ilmenau, Germany — ²Fraunhofer Institute for Solar Energy Systems ISE, Freiburg, 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 layer. Here, in order to improve the crystal quality of the GaP buffer layer grown on Si(100) substrates by MOCVD, we modify the GaP nucleation, which consists of 10 alternating pulses of TBP and TEGa, by substituting the first few selected TEGa pulses with TMAl. Crystal defects in the GaP(100) buffer layers are investigated by electron channeling contrast imaging. GaP buffer layers grown on the GaP nucleation exhibit short misfit dislocations (MDs), and therefore, a high density of threading dislocations (TDs), which are located at the ends of each MD. In contrast, in the GaP buffer layer grown on the AlGaP nucleation the MDs are significantly longer, which results in lower density of TDs. In addition, we find lower density of stacking faults and stacking fault pyramids compared to the GaP buffer layer grown on the GaP nucleation. We conclude that the Al induced in the GaP nucleation layer suppresses defect formation and improves crystal quality of the epilayer. Further studies of reciprocal space map by x-ray diffraction aim to investigate strain in both GaP buffer layers and its correlation to the defect density.