| Autor: |
Gupta, Somya, Simoen, Eddy, Loo, Roger, Madia, Oreste, Lin, Dennis, Merckling, Clement, Shimura, Yosuke, Conard, Thierry, Lauwaert, Johan, Vrielinck, Henk, Heyns, Marc |
| Zdroj: |
ACS Applied Materials & Interfaces; June 2016, Vol. 8 Issue: 21 p13181-13186, 6p |
| Abstrakt: |
An imperative factor in adapting GeSn as the channel material in CMOS technology, is the gate-oxide stack. The performance of GeSn transistors is degraded due to the high density of traps at the oxide-semiconductor interface. Several oxide-gate stacks have been pursued, and a midgap Ditobtained using the ac conductance method, is found in literature. However, a detailed signature of oxide traps like capture cross-section, donor/acceptor behavior and profile in the bandgap, is not yet available. We investigate the transition region between stoichiometric insulators and strained GeSn epitaxially grown on virtual Ge substrates. Al2O3is used as high-κ oxide and either Ge1–xSnxO2or GeO2as interfacial layer oxide. The interface trap density (Dit) profile in the lower half of the bandgap is measured using deep level transient spectroscopy, and the importance of this technique for small bandgap materials like GeSn, is explained. Our results provide evidence for two conclusions. First, an interface traps density of 1.7 × 1013cm–2eV–1close to the valence band edge (Ev+ 0.024 eV) and a capture cross-section (σp) of 1.7 × 10–18cm2is revealed for GeSnO2. These traps are associated with donor states. Second, it is shown that interfacial layer passivation of GeSn using GeO2reduces the Ditby 1 order of magnitude (2.6 × 1012cm–2eV–1), in comparison to GeSnO2. The results are cross-verified using conductance method and saturation photovoltage technique. The Ditdifference is associated with the presence of oxidized (Sn4+) and elemental Sn in the interfacial layer oxide. |
| Databáze: |
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