Remote phonon and surface roughness limited universal electron mobility of In0.53Ga0.47As surface channel MOSFETs

The inversion layer electron mobility in n-channel In"0"."5"3Ga"0"."4"7As MOSFET's with HfO"2 gate dielectric with several substrate impurity concentrations (~1x10^1^6cm^-^3 to ~1x10^1^8cm^-^3) and various surface preparations (HF surface clean, (NH"4)"2S surface clean and PECVD a-Si interlayer with a HfO"2 gate dielectric) have been studied. The peak electron mobility is observed to be strongly dependent on the surface preparation, but the high field mobility is observed to be almost independent of the surface preparation. A detailed analysis of the effective mobility as a function of electric field, substrate doping, and temperature was used to determine the various mobility components (surface roughness, phonon, and coulombic scattering limited mobility components). For the substrates with high doping concentration, the electron mobility at low vertical electric field is dominated by Coulomb scattering from the substrate dopants, whereas, for lower substrate doping the Coulombic scattering is dominated by the disorder induced gap states. Low temperature measurements were used to determine the surface roughness scattering and phonon components. The results show that room temperature mobility of In"0"."5"3Ga"0"."4"7As surface channel MOSFETs with HfO"2 gate dielectric at high electric field is limited primarily by remote phonons whereas the Al"2O"3 gate dielectric is limited by surface roughness scattering.