Relationship between effective mobility and border traps associated with charge trapping in In_0.7Ga_0.3As MOSFETs with various high-κ stacks

The effective mobility and reliability characteristics of In_0.7Ga_0.3As quantum-well (QW) MOSFETs with various high-κ gate stacks and HEMTs with a Schottky gate under bias temperature instability (BTI) stress were investigated. The effective mobilities (μeff) of HEMTs, single-layer Al₂O₃, bilayer Al₂O₃ (0.6 nm)/HfO₂ (2.0 nm), and Al₂O₃ (0.6 nm)/HfO₂ (3.0 nm) were >9000, >6158, >4789, and >4447 cm² V^-1 s^-1 at Ninv = 1.5 × 10¹²/cm², respectively. The maximum effective mobility of In_0.7Ga_0.3As channel MOSFETs was compared with that of In_0.7Ga_0.3As/In_0.48Al_0.52As HEMTs, which are interface and border trap-free FETs. The results showed that the effective channel mobility was sensitive to traps in high-κ dielectrics related to interface trap density and border traps in the oxide. The κVT degradation of the bilayer Al₂O₃/HfO₂ under BTI stress was greater than that of a single Al₂O₃ layer because the HfO₂ layer had a high density of oxygen vacancies which were related to border traps.