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Can the potential barrier across a p-n j...

Can the potential barrier across a p-n junction be measured by simply connecting a voltmeter across the junction ?

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No, it cannot be measured by using a voltmeter. Barrier potential is less than 0.2 V for germanium diode and is less than 0.7 V for silicon. Also there are no free charge carriers which provide 'current ' for working of voltmeter .
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In Fig . V_(0) is the potential barrier across a p-n junction, when no battery is connected across the junction

In Fig. V_(0) is the potential barrier across a p-n junction, when no battery is connected across the junction : .

The potential barrier at PN junction is due to

p-n junction is a semiconductor diode. It is obtained by bringing p-type semiconductor inclose contact with n-type semiconductor. A thin layer is developed at the p-n junction which is devoid of any charge carrier but has immobile ions. It is called depletion layer. At the junction a potential barrier appears, which does not allow the movement of majority charge carriers across the junction in the absence of any biasing of the junction. p-n junction offer low resistance when forward biased and high resistance when reverse biased. Read the above paragaph and answer the following question: (i) Can we measure the potential barrier of p-n junction by putting a sensitive voltmeter across its terminals? (ii) What practical lesson do you draw from the above study?

Can we measure the potential difference of a p-n junction by putting a sensitive voltmeter across its terminals?

Assertion: We can measure the potential barrier of a PN junction by putting a sensitive voltmeter across its terminals. Reason: The current through the PN junction is not same in forward and reversed bias.

Assertion : We cannot meausre that potential barrier of p-n junction by putting a sensitive voltmeter across its terminals. Reason: In the depletion layer, there are no free elctrons or holes and in the absence of forward bias, it offers, infinite, resistance.

Knowledge Check

  • In Fig . V_(0) is the potential barrier across a p-n junction, when no battery is connected across the junction

    A
    1 and 3 both correspond to forward bias of junction
    B
    3 corresponds to forward bias of junction and 1 corresponds to reverse bias of junction
    C
    1 corresponds to forward bias and 3 corresponds to reverse bias of junction
    D
    3 and 1 both correspond to reverse bias of junction

  • In Fig. V_(0) is the potential barrier across a p-n junction, when no battery is connected across the junction : .

    A
    `1` and `3` both correspond is forward bias of junction
    B
    `3` corresponds to forward bias of junction and `1` corresponds to reverse bias junction
    C
    `1` corresponds to forward bias and `3` corresponds to reverse bias junction
    D
    `3` and `1` both correspond to reverse bias and `3` corresponds to revers bias of junction

  • The potential barrier at PN junction is due to

    A
    fixed acceptor and donor ions on either side of the junction
    B
    minority carriers on either side of the junction
    C
    majority carriers on either side of the junction
    D
    both majority and minority carriers on either side of junction