Two-dimensional clusters in SiGe/Si heterostructures and their effect on field effect transistor transport characteristics
| Autor: | V. Kasabyan, A. Thanailakis, A. Christou, D. Girginoudi, N. Georgoulas |
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| Rok vydání: | 1998 |
| Předmět: |
Materials science
Silicon business.industry Transconductance Transistor chemistry.chemical_element Heterojunction High-electron-mobility transistor Substrate (electronics) Condensed Matter Physics law.invention Silicon-germanium chemistry.chemical_compound chemistry law Optoelectronics General Materials Science Field-effect transistor Electrical and Electronic Engineering business |
| Zdroj: | Superlattices and Microstructures. 23:407-411 |
| ISSN: | 0749-6036 |
| Popis: | Heterostructures of Si0.80Ge0.20/Si (100) were grown by pulsed laser deposition consisting of alternating 10 nm SiGe and silicon layers for a total of 10 periods. The presence of alloy clustering at SiGe/Si interfaces was investigated by parallel transport in transistor structures. Photoluminescence line broadening indicated the presence of Ge-rich clusters (20–30 nm) in layers grown at a substrate temperature of 600 ○C using a excimer laser at 248 nm wavelength. The 2D clusters were modeled, assuming a spherical shape and a potential of the form δΔU where δ is the composition variation and ΔU is the disorder potential. A scattering matrix element was derived which included intraband scattering. Transport effects were calculated using Monte Carlo techniques. Of interest was lateral transport in a field effect transistor configuration. Therefore, velocity versus field curves were calculated where electron motion is confined to the 2D-like Si/SiGe interface layers. Using concepts of charge control, current versus voltage relationships were derived. The derived models showed that for the case of a 250 μm conducting channel lateral length with 2D clusters evenly placed at every 10 nm, the transconductance increase is 25% and is a function of both cluster size and separation. In order to measure the effect of clustering, high electron mobility transistors were fabricated with two conducting 2D channels consisting of Si/SiGe/Si grown on high resistivity (100) silicon. Using 0.5 μm gates, a transconductance of 125 mS/mm was obtained in transistors without alloy clustering which decreased to less than 80 mS/mm when alloy clustering was present. The present investigation has related the presence of 2D nano-clusters to device performance and has also shown agreement between the experimental results and theoretical calculations. |
| Databáze: | OpenAIRE |
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