Growth of Metamorphic InGaP for Wide-Bandgap Photovoltaic Junction by MBE

John Simon, Stephanie Tomasulo, Paul Simmonds, Manuel Romero, Minjoo L. Lee

Research output: Contribution to conferencePaperpeer-review


Metamorphic triple-junction solar cells can currently attain efficiencies as high as 41.1%. Using additional junctions could lead to efficiencies above 50%, but require the development of a wide bandgap (2.0-2.2eV) material to act as the top layer. In this work we demonstrate wide bandgap InyGa 1-yP grown on GaAsxP1-x via solid source molecular beam epitaxy. Unoptimized tensile GaAsxP1-x buffers grown on GaAs exhibit asymmetric strain relaxation, along with formation of faceted trenches 100-300 nm deep in the [01-1] direction. Smaller grading step size and higher substrate temperatures minimizes the facet trench density and results in symmetric strain relaxation. In comparison, compressively- strained graded GaAsxP1-x buffers on GaP show nearly-complete strain relaxation of the top layers and no evidence of trenches. We subsequently grew InyGa1-yP layers on the GaAs xP1-x buffers. Photoluminescence and transmission electron microscopy measurements show no indication of phase separation or CuPt ordering. Taken in combination with the low threading dislocation densities obtained, MBE-grown InyGa1-yP layers are promising candidates for future use as the top junction of a multi-junction solar cell.

Original languageAmerican English
Number of pages6
StatePublished - 2010
Externally publishedYes
Event2010 Materials Research Society Symposium - San Francisco, California
Duration: 5 Apr 20109 Apr 2010


Conference2010 Materials Research Society Symposium
CitySan Francisco, California

NREL Publication Number

  • NREL/CP-5200-51229

Other Report Number

  • Paper No. 1268-EE06-04


  • cell efficiency
  • device performance
  • solar cells


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