Minority-carrier response and conductance loss characteristics ofSiNx/Si/Ge/n-GaAs(001)metal–insulator–semiconductor (MIS) structures are presented. The response time of minority carriers withSi(⩽10 Å)/Ge(20 Å) interlayers, as determined by the capacitance–voltage(C–V)method, is several orders of magnitude smaller than those with Si interlayers only. The minority carriers inn-type Si/Ge/GaAs layers respond to even a small ac signal of 1 kHz at room temperature, which is ascribed to the smaller band gap and thus a higher intrinsic carrier concentration of Ge. The minority carriers in theSiNx/Si/Ge/n-GaAsMIS structures respond to a 1 MHz signal at a sample temperature of 230 °C. Temperature-dependentC–Vmeasurements on the GaAs MIS structure with Si/Ge, interlayers revealed the activation energy(Ea)of the minority-carrier recombination to be about 0.58 eV. The conductance loss characteristics ofSiNx/Si/Ge/GaAsstructures indicate a contribution by interface traps responding to slow states, while the fast states are a result of interface defects of theSiNx/Si/GaAsMIS system. ©1997 American Institute of Physics.