In a pn junction diode, |\(\frac{{dV}}{{dT}}\)| is equal to

Barrier potential is defined as:

\({V_0} = \frac{{kT}}{q}\ln \left( {\frac{{{N_A}{N_D}}}{{n_i^2}}} \right)\)

• Built-in potential or contact potential depends on the temperature and doping concentration
• The barrier potential of a p-n junction diode increases as doping concentration is increased.
• The barrier potential of a p-n junction diode decreases as the temperature is increased.

In Ge p-n junction barrier potential decreases by 2.1 mV/ °C

\(\frac{{d{V_0}}}{{dT}} = - 2.1\frac{{mV}}{{^\circ C}}\)

In Si p-n junction barrier potential decreases by 2.3 mV/ °C

\(\frac{{d{V_0}}}{{dT}} = - 2.3\frac{{mV}}{{^\circ C}}\)

In general barrier potential of diode decreases by 2.5 mV/ °C

\(\frac{{d{V_0}}}{{dT}} = - 2.5\frac{{mV}}{{^\circ C}}\)

• A diode can be used as a temperature measuring device, since the forward voltage drop across the diode depends on temperature, as in a silicon bandgap temperature sensor.
• From the Shockley ideal diode equation, it might appear that the voltage has a positive temperature coefficient (at a constant current), but usually, the variation of the reverse saturation current term is more significant than the variation in the thermal voltage term.