Semiconductor diodes, in conjunction with a constant current source, are sometimes used as thermometers. It has been observed experimentally that, within a certain temperature range, the relation between temperature and voltage is almost linear. We show that this linearity is a direct consequence of the constancy of the current flowing through the diode, and that the parameters resulting from a least-squares fit to the experimental data can be used to determine the band gap energy of the semiconductor. We test the validity of our model by comparing our results to measurements on diodes made of germanium and silicon. If we take into account the simplifications used in our model, the results agree well with known values of the energy gaps.
REFERENCES
1.
A.
Sconza
, G.
Torzo
, and G.
Viola
, “Experiment on the physics of the pn junction
,” Am. J. Phys.
62
, 66
–70
(1994
).2.
D. A.
Johnson
, “Demonstrating the light-emitting diode
,” Am. J. Phys.
63
, 761
–762
(1995
).3.
N. S.
Rebello
, C.
Ravipati
, D. A.
Zollman
, and L. T.
Escalada
, “Computer simulation of junction devices
,” Am. J. Phys.
65
, 765
–773
(1997
).4.
P. J.
Collings
, “Simple measurement of the band gap in silicon and germanium
,” Am. J. Phys.
48
, 197
–199
(1980
).5.
B. D.
Sukheeja
, “Measurement of the band gap in silicon and germanium
,” Am. J. Phys.
51
, 72
–72
(1983
).6.
P. R. N.
Childs
, J. R.
Greenwood
, and C. A.
Long
, “Review of temperature measurement
,” Rev. Sci. Instrum.
71
, 2959
–2978
(2000
).7.
M. J.
Moloney
, “Justifying the simple diode equation
,” Am. J. Phys.
54
, 914
–916
(1986
).8.
S. M. Sze, The Physics of Semiconductor Devices (Wiley, New York, 1969).
9.
T.
Haruana
and P. C.
McDonald
, “Evaluation of simple constant current sources for silicon diode thermometers
,” Meas. Sci. Technol.
3
, 713
–717
(1992
).10.
INCOTERM, −10 to 150 °C range, 1 °C scale.
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© 2002 American Association of Physics Teachers.
2002
American Association of Physics Teachers
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