Question

hi, anyone can explain me the impact of temperature on current flow of semiconductor? please.

And please suggest me related courses about semiconductor too. Thx

Answer 1

HFE and Hfe are DC and signal current gain respectively and are temperature sensitive. HFE in typical semiconductor may vary +- 50% at a constant temperature. As temperature increases so does HFE, from -40 degree C to 125 degree C HFE can vary by a product of 3 or 4 times. This is one of the main causes of thermal runaway which must be consider and compensated for in design. Also in BJT's the DC voltage from base to emitter is also temperature sensitive and must be considered, generally its approximated a -2mV/C but in just using that one doesn't really get and understanding of semiconductor operation.

Answer 2

KenLJW has broken it down pretty well. It is very dependent upon the semiconductor. Is there a specific one you are wondering about so that we know it was covered?

Answer 3

In a semiconductor, at 0 K, valence electrons are in filled energy levels (bonds are formed by electron pairs filling the energy levels). They do not respond to an applied electric field to produce current flow. In the presence of an electric field, the electron motion is still random; no net motion in one direction occurs (no current flows). These filled energy levels, which the valence electrons occupy, form the valence band. In order for current to flow, electrons must move from the filled valence band to the empty conduction band. To make this move requires energy, which can be in the form of heat. (Important: the electrons do not move from a "place" in the crystal called the valence band to another "place" called the conduction band. The electrons have the energy associated with the valence band and acquire enough energy to have the energy associated with the conduction band. An energy change occurs, not a position change.) At room temperature, many electrons will have the energy needed to jump to the conduction band. As one electron moves out of the valence band and into the conduction band, a hole (vacancy) is produced in the valence band. Both the electrons in the conduction band and the corresponding holes in the valence band are considered charge carriers. When an electric field is applied to the material, these electrons and holes "drift". The electrons in the conduction band drift in the direction opposite to the applied field, and the holes drift in the same direction as the applied field. Thus, current is produced. As the temperature of the material is increased, more valence electrons acquire sufficient energy to move to the conduction band (producing holes), so more current flows. It is still true that as the temperature is increased, the atoms vibrate more and cause more collisions with the drifting electrons. However, this opposing effect is negligible, compared to the increase in charge carriers.
http://matse1.matse.illinois.edu/sc/b.html