1) As the temperature DECREASES, what happens to the number of unbound electrons
ID: 3162795 • Letter: 1
Question
1) As the temperature DECREASES, what happens to the number of unbound electrons in the
p-type and the n-type materials assuming IEXT remains constant in the p-n junction ?
a) nothing, holes and free electrons densities are due to dopant consentration only
b) the free electron density decreases in the p-type but the free electron density is constant in
the n-type.
c) the free electron density decreases in the n-type but the free electron density is constant in
the p-type
d) the free electron density decreases in both the n-type and p-type
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2) If the ACCEPTOR dopant concentration NA is INCREASED in a p-n junction, what
happens to the hole concentration, assume temperature remains constant ?
a) the hole density increases in both the n-type and p-type
b) the hole density increases in the n-type and decreases in the p-type
c) the hole density increases in the p-type, n-type remains constant.
d) nothing, the number of available free electrons depend on temperature only in both types
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3) As the temperature DECREASES in a p-n junction, what happens to the reverse saturation
current, IS assuming IEXT remains constant ?
a) nothing, IS is due to dopant consentration only
b) IS decreases as temperature decreases because the number of minority carriers decrease.
c) IS increases as temperature decreases because the number of minority carriers increase
d) ID will decrease as IS increases to keep IEXT constant
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4) If the temperature remains constant, what happens to the diffusion current ID and the
built-in barrier voltage if IEXT DECREASES and the p-n junction is forward biased?
a) ID decreases and the barrier voltage decreases
b) ID increases and the barrier voltage increases
c) ID decreases and the barrier voltage increases.
d) ID increases and the barrier voltage decreases.
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5) repeat (4) for a reverse biased p-n junction
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Explanation / Answer
Answering first question
1)As the temperature DECREASES, what happens to the number of unbound electrons in the
p-type and the n-type material
The answer is
p type: no change in the number of holes, assuming NA>>>ni
n type: number of holes increase
so option (c) is correct
c) the free electron density decreases in the n-type but the free electron density is constant in
the p-type
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