P. Harrison

University of Leeds

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Free-electron laser studies of intra-acceptor transitions in GaAs: a potential far-infrared emission system

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (1999)

Matthew P. Halsall P. Harrison H.P.M. Pellemans C. R. Pidgeon

Normal dopant species in III-V semiconductors from shallow donors or acceptors whose atomic-like transitions have energies of the order of 3-20meV which corresponds to the Terahertz region of the spectrum. It has been suggested that these levels could be utilized in an impurity based THz laser system developing a solid-state THz source from such a technology will require engineering of the energy levels to favor radiative recombination. In this paper we report initial experiments to measure the 1s-2p scattering rate for holes bound to Beryllium acceptors in a bulk GaAs epilayer using the European free electron laser facility FELIX. Two absorption lines were studied the so-called D and C lines at 167 cm^-1 corresponding to 1s-2p transitions of the Beryllium acceptors. At high pump powers these lines were saturated and it was possible to perform Pump-probe measurements to observe the recovery of the absorption as a function of time. The temperature dependence of the decays was also measured. The D and C transitions were found to decay with lifetimes of 360ps and 440ps respectively. This represents the firs direct measurement of these transition lifetimes which are much longer than those reported for intersubband scattering. The result are highly encouraging and support the concept of an impurity based Terahertz device for room temperature operation.

Acceptor

Optical Pumping

Atomic electron transition

10.1117/12.361031

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Citations (1)

Time delay in thin slabs with self-focusing Kerr-type nonlinearity

Physical Review A (2008)

Goran Isić V. Milanović J. Radovanović Z. Ikonić D. Indjin

Time delays for an intense transverse electric (TE) wave propagating through a Kerr-type nonlinear slab are investigated. The relation between the bidirectional group delay and the dwell time is derived and it is shown that the difference between them can be separated into three terms. The first one is the familiar self-interference time, due to the dispersion of the medium surrounding the slab. The other two terms are caused by the nonlinearity and oblique incidence of the TE wave. It is shown that the electric field distribution along the slab may be expressed in terms of Jacobi elliptic functions while the phase difference introduced by the slab is given in terms of incomplete elliptic integrals. The expressions for the field-intensity-dependent complex reflection and transmission coefficients are derived and the multivalued oscillatory behavior of the delay times for the case of a thin slab is demonstrated.

Slab

Reflection

Dispersion relation

Dwell time

10.1103/physreva.77.033821

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Citations (17)

Responsivity of quantum well infrared photodetectors at terahertz detection wavelengths

Journal of Applied Physics (2002)

Mazin A. Gadir P. Harrison Richard Soref

A first-principles model of the photocurrent in quantum well infrared photodetectors (QWIPs) is derived. The model examines the responsivity, carrier capture probability and quantum efficiency. It is found that the QWIP sensitivity reaches a plateau below the 10 μm detection wavelength and remains nearly constant from 10 to 50 μm.

Photocurrent

10.1063/1.1467951

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Citations (16)

Intervalley Scattering and the Role of Indirect Band Gap AlAs Barriers: Application to GaAs/AlGaAs Quantum Cascade Lasers

Acta Physica Polonica A (2008)

James Mc Tavish Z. Ikonić D. Indjin P. Harrison

We report on the results of our simulations of Γ -X scattering in GaAs/AlGaAs heterostructures, discussing the importance of the mole fraction, doping density, and lattice and electron temperature in determining the scattering rates.We consider three systems, a single quantum well (for the investigation of Γ -X scattering), a double quantum well (to compare the Γ -X-G and Γ -Γ scattering rates), and an example of a GaAs/AlGaAs mid-infrared quantum cascade laser.Our simulations suggest that Γ -X scattering can be significant at room temperature but falls off rapidly at lower temperatures.One important factor determining the scattering rate is found to be the energy difference between the Γ -and X-states.

10.12693/aphyspola.113.891

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Citations (3)

Radiative Recombination Spectra of Heavily p-Typeδ-Doped GaAs/AlAs MQWs

Acta Physica Polonica A (2008)

J. Kundrotas Aurimas Čerškus Gintaras Valušis M. Lachab Suraj P. Khanna

We present a study of the photoluminescence properties of heavily Be δ-doped GaAs/AlAs multiple quantum wells measured at room and liquid nitrogen temperatures.Possible mechanisms for photocarriers recombination are discussed, with a particular focus on the peculiarities of the excitonic and free carriers-acceptors photoluminescence emissions occurring below and above the Mott metal-insulator transition.Moreover, based on a simple theoretical model, it is found that the critical impurities concentration to observe the Mott transition in the multiple quantum wells samples exhibiting 15 nm wells width and 5 nm thick barrier layers is ≈ 3 × 10 12 cm -2 .

Non-radiative recombination

10.12693/aphyspola.113.963

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Effect of quantum-well confinement on acceptor state lifetime in δ -doped GaAs/AlAs multiple quantum wells

Applied Physics Letters (2003)

Wenwen Zheng Matthew P. Halsall P. Harrison J.‐P. R. Wells I.V. Bradley

Using far-infrared time-resolved spectroscopy, we have investigated the effect of quantum-well confinement on the lifetime of shallow acceptor states in GaAs/AlAs multiple quantum wells with Be δ-doping at the well center. Low-temperature far-infrared absorption measurements clearly show three principal absorption lines due to transitions of Be acceptor states from the ground state to the first three odd-parity excited states, respectively. It is found that the lifetime of excited states monotonically reduces with decreasing quantum-well width, from 350 ps in bulk to 55 ps in a 100 Å well. We suggest that the effect of quantum-well confinement on zone-fold acoustic-phonon modes increases the intra-acceptor scattering rate of acoustic-phonon-assisted relaxation.

Acceptor

Scattering rate

10.1063/1.1623950

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Citations (10)

Quantum Wires and Dots

P. Harrison

This chapter contains sections titled: Further confinement Schrödinger's equation in quantum wires Infinitely deep rectangular wires Simple approximation to a finite rectangular wire Circular cross-section wire Quantum boxes Spherical quantum dots Non-zero angular momentum states Approaches to pyramidal dots Matrix approaches Finite difference expansions Density of states

Quantum wire

Zero (linguistics)

Momentum (technical analysis)

Density matrix

10.1002/0470010827.ch8

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Citations (4)

Experience with the use of DERAKANE vinyl ester‐based GRP in flue gas desulphurization plants

Anti-Corrosion Methods and Materials (1996)

N. Häg P. Harrison

Describes the growth in industrial usage of GRP (glass fibre reinforced plastic) to control corrosion and, in particular, the use of DERAKANE, a vinyl ester used in GRP. Gives examples of its use in Germany, the UK and the USA. Concludes that the experience with GRP based on epoxy vinyl ester resins applications is very positive and it has proved to be a very reliable alternative to more traditional materials.

Vinyl ester

10.1108/eb007388

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Citations (6)

GaN/AlGaN Strain-Balanced Heterostructures for Near-IR Quantum Well Photodetectors

P. Harrison

Abstract : This report results from a contract tasking University of Leeds as follows: The contractor will design, fabricate, and analyze Quantum Well Infrared Photodetectors (QWIP) that detect in the 2-6 micron region. The QWIPs performance will be compared to standard MerCad Telluride (HgCdTe) photodector devices working in the same wavelength region.

Source

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Citations (0)

Carrier scattering

P. Harrison A. Valavanis

To simplify the problem, carrier dynamics may be approximated by two distinct types of process: coherent processes in which wave functions evolve smoothly between their initial and final states; and incoherent, scattering processes. The latter are the focus of this chapter, and are defined as random, infrequent but very rapid events that transfer a carrier between two states. The chapter explains that Fermi's golden rule can be used directly to derive the scattering rates for a given perturbing potential within a two-dimensional system. The intersubband scattering rate can then be averaged over the initial subband distribution is described. The alloy disorder scattering rate is constant with respect to the initial carrier energy. Interface roughness scattering is clearly dependent on the number of interfaces within a system. Carrier scattering in lower-dimensional systems, wires and dots, will be an important issue as they are introduced into future generations of optoelectronic devices.

Scattering rate

Carrier scattering

10.1002/9781118923337.ch10

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Citations (1)