Thick epitaxial GaAsBi layers for terahertz components: the role of growth conditions

A series of 1.5 mu m-thick epitaxial GaAsBi layers have been grown by molecular beam epitaxy on semi-insulating GaAs(100) substrates at temperatures ranging from 300 to 370 degrees C. Complex studies were carried out with a focus to optimize the technological parameters for application of these layers in photoconductive THz components. The investigation of crystalline structure, layer morphology, optical properties, and characteristics of carrier dynamics was performed. Up to 12% of Bi incorporation has been confirmed by optical and structural analyses of GaAsBi layers grown at relatively low temperatures of about 300 degrees C. The carrier lifetimes of these layers varied from 1 to 3 ps. Thick GaAsBi layers grown at higher than 350 degrees C temperatures exhibited higher crystalline quality and longer carrier lifetimes reaching even tens of picoseconds. The Bi content in high-temperature-grown GaAsBi varied from 3 to 7% Bi.