Regensburg 2022 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 30: Poster 2

HL 30.35: Poster

Thursday, September 8, 2022, 11:00–13:00, P3

Effect on Surface Morphology on 1.7eV-GaInAsP-layers on GaAs by surfactant-assisted MOVPE growth — •Ivo Rahlff, Patrick Schygulla, Jens Ohlmann, and David Lackner — Fraunhofer ISE, Freiburg i. B., Germany

III-V-compound multi junction solar cells hold record efficiencies since many decades. Recently, we have demonstrated a GaInP(1.9eV)/AlGaAs(1.44eV)//GaInAsP(1.09eV)/GaInAs(0.74eV) 4-junction wafer bonded solar cell that reaches 47.6% under a concentration of 665 suns (AM1.5d). All subcells are epitaxially deposited by MOVPE. To further increase the realistic efficiency potential above 50% a 6-junction device with the following bandgaps (1.94eV/1.71eV/1.42eV//1.19eV/0.98eV/0.74eV) is suggested. One promising candidate for the 1.71eV junction is GaInAsP. The challenge for this material system lies in the compositional regime between 1.60eV and 1.75eV, where phase separation has been reported.

In this work we investigate the effect of surfactant-assisted growth of GaInAsP alloys on the surface morphology during MOVPE growth. It is found that the GaInAsP growth without surfactant leads to severe surface roughening which is believed to be due to the onset of phase separation. XRD measurements revealed further decreasing tensile strain with increasing TMSb/III ratios which is expected, since the surfactant alters the atomic incorporation. Further investigations on the effect of the opto-electrical quality of the surfactant on the GaInAsP 1.7eV material is currently in progress.