Study of beryllium diffusion mechanisms in InGaAs epitaxial layers grown by CBE

Abstract

The aim of this work is to investigate beryllium diffusion during post-growth annealing in InGaAs epitaxial layers. Indeed, this undesirable diffusion may occur during thermal treatments of InGaAs/InP heterojunction bipolar transistors (HBTs), which can generate a limitation of frequency performances of these devices. Epitaxial structures have been grown by chemical beam epitaxy (CBE). After post-growth rapid thermal annealing (RTA) was performed, secondary ion mass spectrometry (SIMS) was used to characterize the Be depth profiles. In parallel with our experimental study, we consider two models of Be diffusion in InGaAs in the case of point defect nonequilibrium. First, a kick-out diffusion model with neutral Be interstitial species and charged point defects was studied. Then, a combined substitutional-interstitial diffusion model based on simultaneous diffusion by dissociative and kick-out mechanisms is suggested. Good agreements between experimental depth profiles and simulated curves have been obtained.