Proteolytic enzymes of the K-1 strain of Streptomyces griseus obtained from a commercial preparation (Pronase). Purification and characterization of the carboxypeptidase.

Seber, J.F.; Toomey, Thomas P.; Powell, Janet T.; Brew, Keith; Awad, William M.

doi:10.1016/s0021-9258(17)33946-7

Cited by 15 publications

(2 citation statements)

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“…29,30 At higher applied fields a phonon-assisted tunneling mechanism occurs due to a further increase in band bending, leading to additional barrier thinning such that carriers can tunnel through the potential barrier. 31 A P−F effect occurs for charged defects only, while the tunneling mechanism is possible for defects in all charge states.…”

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“…Conduction mechanisms resulting in nonlinear I – V characteristics could either be contact-limited or bulk-limited. − Contact-limited conduction mechanisms include Schottky emission, Fowler–Nordheim tunneling, and direct tunneling. − Bulk-limited conduction mechanisms include Poole–Frenkel emission (PF), hopping conduction, space-charge limited conduction (SCLC), and phonon-assisted tunneling (PAT). − In semiconductors that have a high concentration of deep-level defects, the two leading mechanisms determining conduction are PF and PAT − Band bending occurs as a result of an applied electric field, which in turn results in a reduction in the defect barrier height. , The reduction in the barrier height is associated with an increased ionization rate of charge carriers . Emission of deep-level defects over this potential barrier is due to the PF mechanism, and it occurs at intermediate electric fields. , At higher applied fields a phonon-assisted tunneling mechanism occurs due to a further increase in band bending, leading to additional barrier thinning such that carriers can tunnel through the potential barrier . A P–F effect occurs for charged defects only, while the tunneling mechanism is possible for defects in all charge states.…”

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Charge Transport Mechanisms in a Pb₂P₂Se₆ Semiconductor

Kostina¹,

Hanson²,

Wang³

et al. 2016

ACS Photonics

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Charge transport in semi-insulating Pb 2 P 2 Se 6 single crystals was investigated. The dark current was dominated by the ionization of deep-level defects within the gap of the material, with activation energies between 0.6 and 0.8 eV. A model for charge transport was developed where a continuum of these midgap defect levels determined the conductivity of Pb 2 P 2 Se 6 . Current−voltage characteristics in Pb 2 P 2 Se 6 single crystals showed nonlinear behavior at high voltages. The nonlinear characteristics are attributed to competing Poole−Frenkel emission and phonon-assisted tunneling processes, such that at lower fields the former effect dominates, while at higher electric fields the latter mechanism emerges. Calculated tunneling times in the 250−500 fs range indicate that the deep traps promote weak electron−phonon coupling and that the tunneling involves deep defect levels. Transient multi-terahertz spectroscopy and temperature-dependent photoconductivity measurements reveal signatures of dispersive transport and low mobility on the order of 10 cm 2 /(V s), consistent with a disordered potential energy landscape in Pb 2 P 2 Se 6 . Photoresponse in these crystals is therefore limited by a distribution of trapping and recombination sites within the band gap.

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