Method and apparatus for determining minority carrier diffusion length in semiconductors

Patent · Tue Feb 21 00:00:00 EST 1984

OSTI ID:864900

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 probe electrode immersed in an 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 redox couple solution functions to create a liquid Schottky barrier at the surface of the material. The Schottky barrier is contacted by merely placing the probe in the solution. The redox solution is placed over and in contact with the material to be tested and light is passed through the solution to generate the SPV. To compensate for colored redox solutions a portion of the redox solution not over the material is also illuminated for determining the color compensated light intensity. Steady red light is also used as an optical bias to reduce deleterious space-charge effects that occur in amorphous silicon.

• DOE Contract Number: XG-0-9372-1
• Assignee: RCA Corporation (New York, NY)
• Patent Number(s): US 4433288
• Application Number: 06/280,918
• OSTI ID: 864900
• Country of Publication: United States
• Language: English

Related Subjects

method
apparatus
determining
minority
carrier
diffusion
length
semiconductors
provided
carriers
semiconductor
material
particularly
amorphous
silicon
significantly
constant
magnitude
surface-photovoltage
spv
steady
modulated
illumination
wavelengths
provides
light
excitation
surface
generate
manually
controlled
automatic
servo
maintains
predetermined
value
wavelength
probe
electrode
immersed
electrolyte
solution
containing
redox
couples
preferably
quinhydrone
oxidation-reduction
potential
-1
65
volts
measurement
couple
functions
create
liquid
schottky
barrier
contacted
merely
placing
placed
contact
tested
passed
compensate
colored
solutions
portion
illuminated
color
compensated
intensity
optical
bias
reduce
deleterious
space-charge
effects
occur
carrier diffusion
diffusion length
schottky barrier
solution containing
amorphous silicon
semiconductor material
electrolyte solution
minority carrier
light intensity
predetermined value
minority carriers
reduction potential
reduce deleterious
redox couples
automatic servo
manually controlled
particularly amorphous
redox couple
modulated illumination
oxidation-reduction potential
determining minority
constant predetermined
light excitation
magnitude surface-photovoltage
/324/136/