Absorption properties of GaAsBi based p-i-n heterojunction diodes
The absorption properties of GaAsBi have been investigated using GaAsBi based p–i–n diodes with different bismuth compositions (~2.1 and ~3.4%). The absorption behaviour of GaAsBi as a function of incident photon energy above the band gap follows that of a direct band gap material. With increasing bismuth content, the absorption of photons with energy lower than the band gap in GaAsBi is enhanced, probably due to localized states caused by Bi-related defects. A simplified analysis has been undertaken on the behaviour of absorption as a function of bias voltage. By undertaking photoresponsivity measurements as a function of reverse bias, the background doping type and the minority carriers diffusion lengths in GaAsBi have been determined.