Characterization of Impact Ionization Coefficients in Dilute-Bismuthide InAlBiAs

As a class of highly mismatched alloy, the dilute bismuthides (alternatively, dilute bismides) are III-V semiconductors with bismuth incorporation. Due to its large atomic number, bismuth incorporation leads to large bandgap reduction and high spin-orbit splitting. The extension in operating wavelength of III-V devices through Bi incorporation has led to many dilute bismuthide materials having been explored for infrared devices. However, due primarily to the larger bandgap of the AlAs endpoint compound, Al-containing bismuthide alloys have been comparatively understudied.

Here we present our work on the application of the Al-containing bismuthide InAlBiAs as the charge multiplication region in avalanche photodiodes (APDs). As has been shown previously, the performance of APDs depend heavily on the spin-orbit splitting of the charge multiplication material. Through the introduction of bismuth into conventional APD materials, a strong decrease in the hole impact ionization coefficient can be realized, leading to high performance improvement. Given the highly performing and well-established use of InAlAs-based APDs on InP, the study of bismuth incorporation into devices made from these base materials is of great interest.

In our work on InAlBiAs, measurements of the carrier multiplication show that bismuth incorporation strongly decreases the hole impact ionization coefficient (thereby increasing the ratio of impact ionization coefficient of the electrons to holes at low electric fields) by almost an order of magnitude. These results demonstrate the relevancy of Al-containing bismuthide materials in InP-based optoelectronic devices and motivate their further study.