Method and apparatus for determining minority carrier diffusion length in semiconductors

Patent · Sat Dec 31 23:00:00 EST 1983

OSTI ID:865050

Moore, Arnold R ^[1]

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1. Princeton, NJ

Method and apparatus are provided for determining the diffusion length of minority carriers in semiconductor material, particularly amorphous silicon which has a significantly small minority carrier diffusion length using the constant magnitude surface-photovoltage (SPV) method. Steady or modulated illumination at several wavelengths provides the light excitation on the surface of the material to generate the SPV. A manually controlled or automatic servo system maintains a constant predetermined value of the SPV for each wavelength. A drop of a transparent electrolyte solution containing redox couples (preferably quinhydrone) having an oxidation-reduction potential (E) in the order of +0.6 to -1.65 volts couples the SPV to a measurement system. The drop of redox couple solution functions to create a liquid Schottky barrier at the surface of the material. Illumination light is passed through a transparent rod supported over the surface and through the drop of transparent electrolyte. The drop is held in the gap between the rod and the surface. Steady red light is also used as an optical bias to reduce deleterious space-charge effects that occur in amorphous silicon.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO
• DOE Contract Number: EG-77-C-01-4042
• Assignee: RCA Corporation (New York, NY)
• Patent Number(s): US 4454472
• OSTI ID: 865050
• Country of Publication: United States
• Language: English

Related Subjects

-1
/324/136/204/438/
65
amorphous
amorphous silicon
apparatus
automatic
automatic servo
barrier
bias
carrier
carrier diffusion
carriers
constant
constant predetermined
containing
controlled
couple
couples
create
deleterious
determining
determining minority
diffusion
diffusion length
drop
effects
electrolyte
electrolyte solution
excitation
functions
gap
generate
held
illumination
illumination light
length
light
light excitation
liquid
magnitude
magnitude surface-photovoltage
maintains
manually
manually controlled
material
measurement
method
minority
minority carrier
minority carriers
modulated
modulated illumination
occur
optical
oxidation-reduction
oxidation-reduction potential
particularly
particularly amorphous
passed
potential
predetermined
predetermined value
preferably
provided
provides
quinhydrone
redox
redox couple
redox couples
reduce
reduce deleterious
reduction potential
rod
rod support
rod supported
schottky
schottky barrier
semiconductor
semiconductor material
semiconductors
servo
significantly
silicon
solution
solution containing
space-charge
spv
steady
supported
surface
surface-photovoltage
transparent
value
volts
wavelength
wavelengths