Final PhD Seminar - Structural and electrical properties of In and C + In implanted Ge, Si and Si1-xGex
It is widely accepted that alternative channel materials replacing Si are required to maintain complementary metal oxide semiconductor (CMOS) device performance improvement with scaling beyond the 10-nm technology generation. Ge has been considered a promising candidate as it offers superior carrier mobility compared to Si. Recently, In has been reconsidered as a p-type dopant in Ge given it introduces a shallow accepter energy level, 0.0112 eV above the Ge valence band. Hence we firstly report on the effects of dopant concentration on the structural and electrical properties of In-implanted Ge. The solid solubility of In in Ge was found to be between 0.2 and 0.6 at. %. To meet a more aggressive electrical activation target at advanced device dimensions, C plus In co-doping was applied to achieve an above-equilibrium, metastable solid solubility limit for In in Ge. The low diffusion coefficient of In in Si enables In atoms to form a super steep retrograde channel profile (SSRCP) that boosts device scaling. Thus we also investigated the structural and electrical properties In in Si and Si1-xGex, aiming to combine the positive aspects of In doped Si and In doped Ge. C + In co-doping was again employed to enhance the solid solubility of In in Si1-xGex, as that was previously found to decrease rapidly against substrate Si composition.
The presentation will begin with a brief background introduction of the topic, and then provide a general description of the experimental details, including that of Ion implantation, RBS, TEM, Raman spectroscopy, Hall effect measurement, DFT (density functional theory) and the main structural characterization technique of the thesis, synchrotron-based X-ray absorption fine structure spectroscopy (XAFS). Following that, the structural and electrical properties of four systems will be presented: In implanted Ge, C + In implanted Ge, In implanted Si1-xGex and C + In implanted Si1-xGex. The final part is a summary of the results and an outlook of the potential future work.