Evolution of Stacking Faults Defects During Epitaxial Growths: Role of Surface Kinetics.

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1246-B03-04

Evolution of Stacking Faults Defects During Epitaxial Growths: Role of Surface Kinetics. M. Camarda1, A. La Magna1, A. Canino1 and F. La Via1 1

Consiglio Nazionale delle Ricerche, Istituto di Microelettronica e Microsistemi CNR-IMM, Z.I. VIII Strada 5 I 95121 Catania, Italy

ABSTRACT Three dimensional kinetic Monte Carlo simulations on super-lattices are applied to study the evolution of stacking faults during epitaxial growths. We show that, in the case of misoriented close packed substrates, these defects can either extend throughout the entire epilayer (i.e. extended from the substrate up to the surface) or close in dislocation loops, in dependence of the deposition conditions. We explain this behavior in terms of a surface kinetic competition between these defects and the surrounding crystal: if the local growth rate of the defect is larger compared with that of the perfect crystal the defect will expands, otherwise it will closes. This mechanisms allows to explain several experimental results on homo and hetero epitaxies. INTRODUCTION Epitaxial growth is a commonly used technique to produce high quality monocrystalline semiconductor layers required for electronic devices. The epitaxial layers are usually grown under well controlled deposition conditions in order to obtain a strong reduction of the defects density of the (low quality) substrates. In this growth method, the use of substrates exposing vicinal surfaces, generating a sequence of parallel steps on the crystal surface, can help in preventing island nucleation and reduce the surface roughness. This technique is called "stepcontrolled epitaxial growth" or step-flow. The step-flow growth also allows, when close packed structures are processed (i.e. in the case of many compound semiconductors such as SiC, GaN, GaAs, etc.), to hinder the generation and propagation of stacking faults and polytype inclusions[1]. When this growth technique is applied, a slow (quasi-equilibrium) process is the usual prescription to growth high quality crystal. This prescription is theoretically supported by the calculated, strictly positive, formation energies of the defects. However, the kinetics of the crystal healing during epitaxial growths has not been so far investigated in details. This issue can be especially intriguing in the case of stacking faults in close packed structures which can have very low formation energies[2]. Moreover, some recent experimental findings make questionable the low growth rate prescription since crystals with higher qualities were obtained at higher growth rates[3].

Fig.1 Evolution of a SL-SSF defect. The different colors represent the three different particles sites A,B or C. Top the initial configuration of the substrate, Lbox and Linit are, respectively, the computational box and initial defect extension along the [-12-10] direction. Bottom the system after a short-time evolution. The presence of the defect is visible underneath the surface. In the past the step-flow growth mode has been studied applying either continuous m