Research on lattice-mismatched semiconductor layers. Progress report No. 2, 16 August 1977-15 May 1978. [Al/sub x/Ga/sub 1-x/As/sub 1-y/Sb/sub y/]
Investigations of the Al/sub x/Ga/sub 1-x/As/sub 1-y/Sb/sub y/ quaternary alloy have shown that compositions necessary for a two-junction stacked solar cell can be grown by LPE. Aluminum concentrations of 88 mole% have been grown in an alloy containing 16 mole% Sb. For a constant Al concentration in the solution, the addition of Sb causes Al incorporation in the solid to decrease. Antimony behavior is similar to that observed in the GaAsSb ternary system. Lattice constant grading using Al depletion to change As activity has been used to continuously grade from GaAs to Al /sub 01/Ga /sub 99/As /sub 84/Sb /sub 16/. Layers of GaAs /sub 84/Sb /sub 16/ have been routinely grown on the graded layer. The best orientation for combining good growth rate, surface morphology and solution removal has been the GaAs (111)A surface. Growth rates for the conditions used are in the order (100) > (111)A > (111)B. Etch-pit densities are normally greater than or equal to 10/sup 6/ cm/sup -2/ after grading and sometimes inhomogeneously distributed. Etch-pit studies during the early stages of growth suggest that dislocation bunching occurs at this stage. Tin doping of GaAsSb is shown to be dependent upon which side of the pseudobinary growth occurs. The net electron concentration for a given X/sub Sn//sup l/ is observed to be higher when growth is from an Sb-rich solution. Complete 1.15-eV solar cells consisting of Al /sub 6/Ga /sub 4/As /sub 85/Sb /sub 15//GaAs /sub 84/Sb /sub 16//graded AlGaAsSb/GaAs(111)A have been fabricated and tested. The maximum quantum efficiency in the cells tested to date has been 25%. GaAsSb p-n junctions with low leakage currents over areas as large as 0.68 cm/sup 2/ have been grown on continuously graded layers.
- Research Organization:
- Varian Associates, Inc., Palo Alto, CA (USA)
- OSTI ID:
- 5963581
- Report Number(s):
- SAN-1250-2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
140501* -- Solar Energy Conversion-- Photovoltaic Conversion
36 MATERIALS SCIENCE
360601 -- Other Materials-- Preparation & Manufacture
ALLOYS
ALUMINIUM ALLOYS
ANTIMONY ALLOYS
ARSENIC ALLOYS
ARSENIC COMPOUNDS
ARSENIDES
CARRIER DENSITY
CARRIER MOBILITY
CRYSTAL DEFECTS
CRYSTAL DOPING
CRYSTAL STRUCTURE
DIRECT ENERGY CONVERTERS
DISLOCATIONS
ENERGY GAP
EPITAXY
ETCHING
FABRICATION
GALLIUM ALLOYS
GALLIUM ARSENIDE SOLAR CELLS
GALLIUM ARSENIDES
GALLIUM COMPOUNDS
GRADED BAND GAPS
JUNCTIONS
LATTICE PARAMETERS
LINE DEFECTS
MICROSTRUCTURE
MOBILITY
MORPHOLOGY
ORIENTATION
P-N JUNCTIONS
PERFORMANCE
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PNICTIDES
QUANTITY RATIO
SEMICONDUCTOR JUNCTIONS
SOLAR CELLS
SUBSTRATES
SURFACE FINISHING