Minority-carrier characteristics of SiNx/GaAs metal–insulator–semiconductor structures with Si/Ge interlayers

Abstract

Minority-carrier response and conductance loss characteristics of SiNx/Si/Ge/n-GaAs(001) metal–insulator–semiconductor (MIS) structures are presented. The response time of minority carriers with Si(⩽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 in n-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 the SiNx/Si/Ge/n-GaAs MIS structures respond to a 1 MHz signal at a sample temperature of 230 °C. Temperature-dependent C–V measurements 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 of SiNx/Si/Ge/GaAs structures indicate a contribution by interface traps responding to slow states, while the fast states are a result of interface defects of the SiNx/Si/GaAs MIS system.