Modeling of dopant incorporation, segregation, and ion/surface interaction effects during semiconductor film growth by molecular beam epitaxy and plasma-based techniques

Abstract

A model describing the incorporation of dopants into single crystals films grown by molecular beam epitaxy (MBE) is presented. The model accounts for dopant surface segregation during deposition and allows dopant incorporation probabilities and depth profiles to be calculated as a function of film growth conditions (e.g. deposition rate, dopant beam flux, and growth temperature, T_s). Input data to the model include thermodynamic parameters such as the free energy of segregation and dopant-surface binding energies together with kinetic parameters such as incident fluxes and dopant diffusivities. The model is applied here to the case of thermal doping during MBE with impurities exhibiting strong surface segregation and near-unity incorporation probabilities, σ, as well as those exhibiting both strong segregation and temperature-dependent σ values. In addition, an extension of the model is used to account for accelerated-ion doping during MBE. Calculated values of σ(T_s) and calculated depth profiles were found to agree very well with available experimental results in these cases. Finally, dopant incorporation data for epitaxial semiconductors deposited in glow discharge environments in which the growing film is bombarded by relatively large fluxes of inert gas ions as well as by ionized dopant species are presented and discussed. The results in this case are similar to low flux ion doping in MBE but with the additional effects of preferential sputtering and collisional mixing.