GaAs_1-xBi_xおよびGaAs/GaAs_1-xBi_xヘテロ界面における局在準位

抄録

The dilute bismuthide III-V semiconductor GaAs_1-xBi_x alloys have unusual properties owing to large bowing of the band gap energy caused by Bi incorporation and a reduction of the temperature coefficients of the band gap. Deep- and shallow-level defects in device-quality GaAs_1-xBi_x (χ ≤ 5.4%) are investigated. Deep- and shallow-level defects behave as non-radiative recombination centers and electrical carrier traps. The Bi-related localized states induced by the interaction between spatially localized Bi states and the valence band of GaAs are continuously located up to ∼90meV from the valence band with a density of ∼1 × 10¹⁷cm^-3. In spite of concerns about the degradation of the hole mobility in GaAs_1-xBi_x due to scattering at these Bi-related localized states near the valence band, the p-type doping masks the contribution of the Bi-related states to the hole mobility, and a high hole mobility of 200 cm²V^-1s^-1 is demonstrated. Despite low-temperature growth, the deep-level trap density in GaAs_1-xBi_x is suppressed on the order of 10¹⁵cm^-3 comparable to GaAs because of a surfactant-like effect of the Bi atoms. While the interface state density of ∼8 × 10¹¹cm^-2eV^-1 in a GaAs/GaAs_1-xBi_x heterointerface cannot be reduced by annealing, it can be reduced by half by the insertion of a Bi graded layer into the heterointerface.