Collection velocity of excess minority carriers at metal-semiconductor contacts in solar cells

Journal Article · Mon Nov 01 00:00:00 EST 1976 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.322503· OSTI ID:7260939

Card, H C

An expression for the collection velocity S of excess minority carriers at metal-semiconductor contacts is derived analytically for both the Schottky barrier and the Ohmic contact. Short-circuit conditions are assumed, appropriate to the collection of optically generated minority carriers by Schottky barriers or Ohmic contacts in solar cells or photodetectors. This analysis is then applied to the calculation of S for the materials of primary interest in solar cells (Si, GaAs, and CdS). It is found that S increases with the minority-carrier mobility and with the doping concentration according to Sapprox...mu../sub p/ N/sup 1///sup 2//sub d/ (for the contact: metal--n-type semiconductor), but is independent of the barrier height phi/sub b/ or diffusion potential V/sub d//sub o/, provided qV/sub d//sub o/approximately-greater-than few KT. This means that, for Ohmic contacts, S depends on whether the contact is achieved by using high N/sub d/ (for which Sapprox. =10/sup 9/ cm/s for Si cells) or by low phi/sub b/ but moderate N/sub d/ (Sapprox. =10/sup 7/ cm/s for Si cells). More generally, S varies between approx. =10/sup 6/ cm/s (for CdS cells, low N/sub d/) and approx. =10/sup 10/ cm/s (p-type GaAs cells, high N/sub d/). Also defined are the conditions under which the finite collection velocity at the contact limits the collected minority-carrier current. (AIP)

• Research Organization: Department of Electrical Engineering and Computer Science, Columbia University, New York, New York 10027
• OSTI ID: 7260939
• Journal Information: J. Appl. Phys.; (United States), Vol. 47:11, Issue 11
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
SOLAR CELLS
EFFICIENCY
CADMIUM SULFIDES
CARRIER MOBILITY
ELECTRIC CONTACTS
FERMI LEVEL
GALLIUM ARSENIDES
INTERFACES
LIFETIME
PHOTODETECTORS
RECOMBINATION
SCHOTTKY BARRIER DIODES
SILICON
SOLAR COLLECTORS
ARSENIC COMPOUNDS
ARSENIDES
CADMIUM COMPOUNDS
CHALCOGENIDES
DIRECT ENERGY CONVERTERS
ELECTRICAL EQUIPMENT
ELEMENTS
ENERGY LEVELS
EQUIPMENT
GALLIUM COMPOUNDS
INORGANIC PHOSPHORS
MOBILITY
PHOSPHORS
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PNICTIDES
SEMICONDUCTOR DEVICES
SEMICONDUCTOR DIODES
SEMIMETALS
SULFIDES
SULFUR COMPOUNDS
140501* - Solar Energy Conversion- Photovoltaic Conversion