Depletion Region shrinks with increased temperature

jaxper

Hi,

Quick question. In a PN junction, the depletion region will shrink with an increase in temperature. Why is that? Is the Fermi energy of the p and n semiconductors a function of temperature?

Thanks!

Jax

mmwave

If the depletion region width shrinks as temperature increases its because the density of carriers is increasing.

The applied voltage determines the amount of charge stored in the junction. The cross sectional area is fixed so the depletion width is whatever value is needed so the area of the region times the number of charge carriers per cm^3 equals the required charge. If the density of charge carriers increases, then less width is required to store the required charge.

In actual practice though, the density of charge carriers is determined by the density of dopant atoms over a broad range of temperatures (say 100 K to 350 K). So there should be very little change in depletion width with temperature.

Mark Calley

Hello,
Based on mmwave's answer that PN junction depletion width decreases with temperature (I assume junction is reverse biased), then will junction capacitance therefore increase with temperature? If so, is there any appreciable change in capacitance with temperature?
Thx