On a possibility of the appearance of two minima in the temperature dependence of mobility

Abstract

We consider a semiconductor doped with shallow donors and deep acceptors. At low temperatures the scattering of the charge c a r r i e r s is mainly due to the impurities, which may be both neutral and charged and may form dipole centres (donor-acceptor pairs). On increasing the temperature (T) the charge states of impurities vary: the neutral impurities (concentration N1) become ionized while the dipole scattering centres N are gradually transformed into single ions (N3) due to a decrease of the electron wavelength. Thus, increasing the temperature leads to the decrease of the scattering efficiency by neutral and dipole centres, while the efficiency by single ion scattering becomes more and more efficient. 2In this note the temperature behaviour of the charge c a r r i e r mobility is considered for compensated semiconductors (for example GaAs). We take into account the above-mentioned variation of the states of scattering centres. Using the results of /1,2/ the corresponding scattering centre concentrations are written a shere N E a r e the free electron concentration and energy, respectively, b = (E /E) Eo = h /2mqtO is the free electron energy with L = Ro; Ro is the average distance between neighbouring impurities. F o r simplicity we assume that a t E 7 Eo the charge c a r r i e r s are scattered as if by single ions, while a t E < E the scat-