Positive solution: In fact, semiconductors with high resistivity are not necessarily intrinsic semiconductors.
First, we must figure out the essence of intrinsic semiconductors. Any semiconductor in which both types of carriers have the same effect on conduction is called an intrinsic semiconductor. Therefore, a semiconductor whose equilibrium electron concentration and equilibrium hole concentration are equal is an intrinsic semiconductor; therefore, the condition of an intrinsic semiconductor is: no=po=ni.
It can be seen that undoped semiconductors are indeed intrinsic semiconductors, but doped semiconductors can also be transformed into intrinsic semiconductors at high temperatures. Because the majority carrier is mainly provided by doping, when the impurity is fully ionized, the majority carrier concentration basically does not change with temperature; and because the minority carrier is completely generated by the intrinsic excitation, and the intrinsic excitation It is a thermal excitation process, and the minority carrier concentration generated will increase exponentially with temperature. Therefore, when the temperature rises to a certain level, the minority carrier concentration will be equal to the majority carrier concentration. At this time, the semiconductor becomes an intrinsic semiconductor, but the conductivity of this intrinsic semiconductor is very good.
In addition, undoped intrinsic semiconductors, because the carriers are generated by thermal excitation, are very small at room temperature, and their resistivity is indeed high. However, if a so-called compensation semiconductor doped with a large number of donors and acceptors at the same time, due to the compensation (cancellation) effect of impurities, the effective majority carrier concentration is small (equal to the difference between the two impurity concentrations), so the semiconductor will also It has a high resistivity, but this is by no means an intrinsic semiconductor.