Device performance of light emitting transistors with C-doped and Zn-doped base layers

N-InP/p-InAlGaAs/N-InAlAs light emitting transistors (LETs) operating at ~1.55 mum were investigated. Both carbon (C) and zinc (Zn) were used as the p-type dopant of the base layers. It was found that C stays in place while Zn diffuses into the emitter and the base active region, resulting in compromised electrical performance and light output intensity. On the other hand, due to a short minority carrier lifetime, LETs with the C-doped base have a much smaller current gain than LETs with the Zn-doped base.