Effective Mass Filtering Research Articles

Multi‐Collector SIMS Determination of Trace Lanthanides in Zircon

A method is presented for the determination of rare earth elements (REE) in zircon (ZrSiO4) using a multi‐collector equipped ion‐microprobe operating at moderately high mass resolution (M/ΔM ˜ 3900). The low abundance light REE (La‐Eu) were measured simultaneously in six ion counting electron multipliers, reducing analytical time to less than half of that in a monocollection routine. Effective mass filtering, moderate energy filtering and careful set up of detector parameters in order to minimise background counts, yielded a highly coherent set of analyses from the 91500 zircon reference sample.

Resonant tunneling through double barriers, perpendicular quantum transport phenomena in superlattices, and their device applications

New results on the physics of tunneling in quantum well heterostructures and its device applications are discussed. Following a general review of the field in the Introduction, in the second section resonant tunneling through double barriers is investigated. Recent conflicting interpretations of this effect in terms of a Fabry-Perot mechanism or sequential tunneling are reconciled via an analysis of scattering. It is shown that the ratio of the intrinsic resonance width to the total scattering width (collision broadening) determines which of the two mechanisms controls resonant tunneling. The role of symmetry is quantitatively analyzed and two recently proposed resonant tunneling transistor structures are discussed. The third section deals with perpendicular transport in superlattices. A simple expression for the low field mobility in the miniband conduction regime is derived; localization effects, hopping conduction, and effective mass filtering are discussed. In the following section, experimental results on tunneling superlattice photoconductors based on effective mass filtering are presented. In the fifth section, negative differential resistance resulting from localization in a high electric field is discussed. In the last section, the observation of sequential resonant tunneling in superlattices is reported. We point out a remarkable analogy between this phenomenon and paramagnetic spin resonance. New tunable infrared semiconductor lasers and wavelength selective detectors based on this effect are discussed.

Effective mass filtering: New quantum photoconductivity in superlattices

Effective mass filtering: New quantum photoconductivity in superlattices

Effective mass filtering: new quantum photoconductivity in superlattices

Effective mass filtering: new quantum photoconductivity in superlattices

New Quantum Photoconductivity and Large Photocurrent Gain by Effective-Mass Filtering in a Forward-Biased Superlatticep−nJunction

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Quantum photoconductive gain by effective mass filtering and negative conductance in superlattice pn junctions

Abstract We report a new quantum type photoconductivity, accompanied by a large current gain (>2×10 3 ) in a pn junction with an Al 0.48 In 0.52 As (23A°) Ga 0.47 In 0.53 As (49A°) superlattice in the n layer, forward biased beyond flat band. The high photoconductive gain is caused by the fact that electrons are transported by miniband conduction while holes are mainly localized in the wells (effective mass filtering). When the pn junction instead is reversed biased two peaks are observed in the photo- current vs voltage characteristics. These occur at voltages such that the potential energy difference between two adjacent wells of the superlattice. is equal respectively to the width of the first and second miniband, in excellent agreement with the Dohler-Tsu-Esaki theory. This type of negative differential resistance occurs when the transport mechanism changes from miniband conduction to hopping.

IVA-1 giant amplification of the photocurrent in a superlattice by effective mass filtering

IVA-1 giant amplification of the photocurrent in a superlattice by effective mass filtering

New quantum photoconductivity and large photocurrent gain by effective-mass filtering in a forward-biased superlattice p-n junction.

New quantum photoconductivity and large photocurrent gain by effective-mass filtering in a forward-biased superlattice p-n junction.

Effective mass filtering: Giant quantum amplification of the photocurrent in a semiconductor superlattice

We report the first observation of an extremely large photocurrent amplification phenomenon at very low voltages in a superlattice of Al0.48In0.52As (35 Å)/Ga0.47In0.53As (35 Å), grown by molecular beam epitaxy. Responsivities at λ=1.3 μm are as high as 4×103 A/W at 1.4 V corresponding to a current gain of 2×104. Significant gains (≂50) were obtained at voltages as low as 20 mV. The detectivity D* at λ=1.3 μm and 1-kHz modulation frequency is 1011 (cm Hz1/2/W) at 0.2-V bias. This effect, which represents a new quantum type photoconductivity, is caused by the large difference in the tunneling rates of electrons and holes through the superlattice barriers, associated with their large effective mass difference (effective mass filtering). Superlattice effective mass filters represent a new class of low voltage, high gain photodetectors. A unique feature, which makes them potentially extremely versatile, is the ability to tune the gain and gain-bandwidth product over a wide range by varying the superlattice period and/or duty factor.