Why does an extrinsic semiconductor behave like an intrinsic semiconductor at high temperature?

With the increase in temperature, the concentration of minority carriers starts increasing. Eventually, a temperature is reached called the critical temperature (85° C in case of germanium and 200° C in case of silicon) when the number of covalent bonds that are broken is very large and the number of holes is approximately equal to number of electrons. The extrinsic semiconductor now behaves essentially like an intrinsic semi-conductor.