Tuesday, February 25, 2020

Electron transport lifetimes in InSb/Al1-x In x Sb quantum well 2DEGs

We report magnetotransport measurements of InSb/Al1-x In x Sb modulation doped quantum well (QW) structures and the extracted transport $({\tau }_{{\rm{t}}})$ and quantum $({\tau }_{{\rm{q}}})$ lifetime of carriers at low temperature $(\lt 2\,{\rm{K}}).$ We consider conventional transport lifetimes over a range of samples with different doping levels and carrier densities, and deduce different transport regimes dependent on QW state filling calculated from self-consistent Schrödinger–Poisson modelling. For samples where only the lowest QW subband is occupied at electron densities of $2.13\times {10}^{11}$ cm−2 and $2.54\times {10}^{11}$ cm−2quantum lifetimes of ${\tau }_{{\rm{q}}}\approx 0.107$ ps, and ${\tau }_{{\rm{q}}}\approx 0.103$ ps are extracted from Shubnikov–de Haas oscillations below a magnetic field of $0.8$ T. The extracted ratios of transport to quantum lifetimes, ${\tau }_{{\rm{t}}}/{\tau }_{{\rm{q}}}\approx 17$ and ${\tau }_{{\rm{t}}}/{\tau }_{{\rm{q}}}\approx 20\,\,$are similar to values reported in other binary QW two-dimensional electron gas systems, but are inconsistent with predictions from transport modelling which assumes that remote ionized donors are the dominant scattering mechanism. We find the low ${\tau }_{{\rm{t}}}/{\tau }_{{\rm{q}}}$ ratio and the variation in transport mobility with carrier density cannot be explained by reasonable levels of background impurities or well width fluctuations. Thus, there is at least one additional scattering mechanism unaccounted for, most likely arising from structural defects.

Source:IOPscience

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Wednesday, February 19, 2020

Deep level transient spectroscopy measurements on heterostructure InSb/InAlSb diodes

Deep level transient spectroscopy (DLTS) measurements have been conducted on MBE-grown heterostructure InSb/In1−xAlxSb diodes. The measurements were conducted in the temperature range 10–130 K and two majority carrier (electron) traps, labelled E1 and E2, have been observed. A trap signature has been produced from the DLTS spectra for both traps. The activation energies determined from Arrhenius plots of the peak temperatures as a function of rate window for E1 and E2 were 17 meV and 79 meV, respectively. The apparent capture cross-sections and concentrations for E1 and E2 have also been measured.

Source:IOPscience

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Wednesday, February 12, 2020

PTCDA molecules on an InSb(001) surface studied with atomic force microscopy

PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride) molecular structures assembled on an InSb(001) c(8 × 2) reconstructed surface have been studied using frequency modulated atomic force microscopy. The high-resolution imaging of the structures is possible through repulsive interactions, using the constant height scanning mode. During initial stages of growth the [110] diffusion channel dominates as indicated by formation of long PTCDA molecular chains parallel to the [110] crystallographic direction on the InSb surface. For a single monolayer coverage a wetting layer of PTCDA is formed. Finally it is shown that the PTCDA/InSb is a promising system for building molecular nanostructures by manipulation of single molecules with the AFM tip.

 Source:IOPscience

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