Assessment of beryllium out-diffusion in AlGaAs/GaAs heterojunction bipolar transistors using low-temperature photoluminescence technique

Low-temperature photoluminescence (PL) is used for the investigation of beryllium (Be) dopant out-diffusion in AlGaAs/GaAs abrupt single-heterojunction bipolar transistors (HBTs). The degree of Be out-diffusion into the emitter from a Be-doped base can be estimated based on the band gap narrowing effect (BGNE). The measured current gain and emitter-base turn-on voltage of HBTs fabricated on wafers with different growth conditions were found to correlate well with the PL results.