A Generalized Model of Beryllium Diffusion in InGaASs Epitaxial Structures Under Point Defect Nonequilibrium Conditions

ABSTRACTBeryllium diffusion during post-growth annealing is investigated in InGaAs epitaxial layers. Indeed, this undesirable diffusion may occur during thermal treatments of InGaAs/lnP Heterojunction Bipolar Transistors (HBT's), which can generate a limitation of frequency performances of these devices. Epitaxial structures have then been grown, one set by Chemical Beam Epitaxy (CBE), and another one by Gas Source Molecular Beam Epitaxy (GSMBE). The post-growth Rapid Thermal Annealing (RTA) was then performed, and Secondary Ion Mass Spectrometry (SIMS) has been used to characterize the Be depht profiles.In parallel with our experimental study, we propose two models of Be diffusion in InGaAs in the case of point defect nonequilibrium. First, a Kick-out Diffusion model considering neutral Be interstitial species and charged point defects has been studied. Then, a Generalized Substitutional-Interstitial Diffusion model based on simultaneous diffusion by Dissociative and Kick-out mechanisms is proposed. Good agreements between experimental depth profiles and simulated curves have been obtained.