Modeling of Be Diffusion in InGaAs Epitaxial Structures

Abstract

ABSTRACTThe subject of this work is the simulation of Be diffusion during post-growth Rapid Thermal Annealing (RTA) of InGaAs epitaxial layers grown by Chemical Beam Epitaxy (CBE). This diffusion may occur during thermal treatments of InGaAs/InP Heterojunction Bipolar Transistors (HBT's), which contributes to limit the frequency performances of these devices. In order to characterize the Be depth profiles, Secondary Ion Mass Spectrometry (SIMS) has been used. The concentration dependent diffusivity has been covered to perform an improved data fitting of Be diffusion profiles. In a first step, the solid state diffusion mechanisms have been developed, including the Substitutional-Interstitial Diffusion (SID) and, in particular, Kick-out mechanism. To explain the observed concentration profiles and related diffusion mechanisms, a Generalized Substitutional-Interstitial Diffusion model is proposed. A simultaneous diffusion by Dissociative and Kick-out mechanisms is suggested. Good agreements between experimental depth profiles and simulated curves have been obtained.