InSb wafer: March 2018

Tuesday, March 13, 2018

Evaluation of complex conductivity in a circularly polarized field by terahertz time-domain reflection spectroscopy with a phase shifter

We propose a smart technique for directly evaluating complex conductivity in a circularly polarized field with no polarimeter by time-domain reflection spectroscopy using a terahertz (THz) phase shifter and a polarized beam splitter. We performed THz time-domain spectroscopy on a doped InSb wafer under a magnetic field with a δ-phase shifter based on parallel metal waveguides. Despite the π/2 phase shifter with low accuracy, we obtained the conductivity spectrum shifted by cyclotron frequency while maintaining a Drude-like spectral shape. This technique paves the way for new magneto-optical spectroscopy methods.

Source:IOPscience

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Monday, March 5, 2018

Characterization of Al2O3/InSb/Si MOS diodes having various InSb thicknesses grown on Si(1 1 1) substrates

This paper discusses the capacitance–voltage (C–V) characteristics of Al2O3/InSb/Si (1 1 1) MOS diodes grown using MBE via InSb bi-layer with special care to the surface reconstruction. This growth technique is based on our finding that the InSb layer grown on a Si (1 1 1) substrate is rotated by 30° with respect to the substrate under certain initial conditions. This rotation drastically reduces the lattice mismatch from 19.3% to 3.3%, and improves the crystal quality of an InSb layer. To investigate the possibilities of InSb MOSFETs on Si substrates, we fabricated MOS diodes having an Al2O3 insulator film deposited by atomic layer deposition. C–V characteristics were measured both at RT and 77 K. It was found that the InSb grown on Si shows a degraded C–V curve compared to the InSb substrate, even though the mobility of the grown layer is quite high. We also investigated the effects of InSb thickness on the C–V characteristics of the MOSFETs. It was found that the quality of MOS diodes first degrades when decreasing the InSb thickness from 1 μm to 50 nm; further reduction of the InSb thickness improves it again. It was demonstrated that the MOS diode having a 10 nm InSb layer shows a good C–V curve, which is comparable to that of the InSb substrate. Finally, we discussed the possibility of the InSb/Si pseudomorphic MOSFETs.