Reduction of Crosshatch Roughness and Threading Dislocation Density in Metamorphic GaInP Buffers and GaInAs Solar Cells
Surface crosshatch roughness typically develops during the growth of lattice-mismatched compositionally graded buffers and can limit misfit dislocation glide. In this study, the crosshatch roughness during growth of a compressive GaInP/GaAs graded buffer is reduced by increasing the phosphine partial pressure throughout the metamorphic growth. Changes in the average misfit dislocation length are qualitatively determined by characterizing the threading defect density and residual strain. The decrease of crosshatch roughness leads to an increase in the average misfit dislocation glide length, indicating that the surface roughness is limiting dislocation glide. Growth rate is also analyzed as a method to reduce surface crosshatch roughness and increase glide length, but has a more complicated relationship with glide kinetics. Using knowledge gained from these experiments, high quality inverted GaInAs 1 eV solar cells are grown on a GaInP compositionally graded buffer with reduced roughness and threading dislocation density. The open circuit voltage is only 0.38 V lower than the bandgap potential at a short circuit current density of 15 mA/cm{sup 2}, suggesting that there is very little loss due to the lattice mismatch.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
- DOE Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1046870
- Report Number(s):
- NREL/JA-5200-54042; JAPIAU; TRN: US201215%%563
- Journal Information:
- Journal of Applied Physics, Vol. 111, Issue 10; Related Information: Article No. 103528; ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
BUFFERS
CURRENT DENSITY
DEFECTS
DISLOCATIONS
ELECTRIC POTENTIAL
ELECTRICAL FAULTS
ENERGY GAP
GALLIUM ARSENIDES
GALLIUM COMPOUNDS
INDIUM COMPOUNDS
KINETICS
PARTIAL PRESSURE
PHOSPHINES
ROUGHNESS
SLIP
SOLAR CELLS
STRESSES
virtual substrates
solar cell
growth conditions
glide length