Search results for "semiconductor material"

External noise effects on the electron velocity fluctuations in semiconductors

2008

We investigate the modification of the intrinsic carrier noise spectral density induced in low-doped semiconductor materials by an external correlated noise source added to the driving high-frequency periodic electric field. A Monte Carlo approach is adopted to numerically solve the transport equation by considering all the possible scattering phenomena of the hot electrons in the medium. We show that the noise spectra are strongly affected by the intensity and the correlation time of the external random electric field. Moreover this random field can cause a suppression of the total noise power.

Steady light from quantum dots, at last. But how?

2009

The role of nonlinear optical absorption in narrowband difference-frequency terahertz-wave generation

2010

We present a general analysis of the influence of nonlinear optical absorption on terahertz generation via optical difference frequency generation, when reaching for the quantum conversion efficiency limit. By casting the equations governing the process in a suitably normalized form, including either two-photon- or three-photon-absorption terms, we have been able to plot universal charts for phase matched optical-to-terahertz conversion for different values of the nonlinear absorption coefficients. We apply our analysis to some experiments reported to date, in order to understand to what extent multiphoton absorption could have played a role and also to predict the maximum achievable conver…

Rotating magnetic fields as a means to control the hydrodynamics and heat transfer in single crystal growth processes

1999

The paper discusses a possibility to use different types of rotating magnetic fields (RMF) and combinations of these to control the hydrodynamics and heat/mass transfer in the processes of bulk semiconductor single crystal growth. Some factors contributing to the efficiency of RMF and their influence on different technologies are analyzed. Their specific practical application is illustrated by some examples.

Studio della Nonlinearità Quadratica di Zincoblende per la Generazione di TeraHertz in Guida d'Onda: un Confronto di Cristalli Differenti

2009

DFG TeraHertz generation can approach the quantum efficiency limit with much lower peak powers than bulk experiments. We give details on the model and on the waveguide geometry.

Studio della nonlinearità quadratica di zincoblende per la generazione di TeraHertz in guida d'onda: un confronto di cristalli differenti

2009

DFG TeraHertz generation can approach the quantum efficiency limit with much lower peak powers than bulk experiments. We give details on the model and on the waveguide geometry.

Exploiting the optical quadratic nonlinearity of zinc-blende semiconductors for guided-wave terahertz generation: A material comparison

2010

We present a detailed analysis and comparison of dielectric waveguides made of CdTe, GaP, GaAs and InP for modal phase matched optical difference frequency generation (DFG) in the terahertz domain. From the form of the DFG equations, we derived the definition of a very general figure of merit (FOM). In turn, this FOM enabled us to compare different configurations, by taking into account linear and nonlinear susceptibility dispersion, terahertz absorption, and a rigorous evaluation of the waveguide modes properties. The most efficient waveguides found with this procedure are predicted to approach the quantum efficiency limit with input optical power in the order of kWs.

Photocatalytic membrane reactors: fundamentals, membrane materials and operational issues

2013

Abstract: This chapter reports the properties of semiconductor materials used in heterogeneous photocatalysis together with a comparison of heterogeneous photocatalytic systems and a brief description of the types of membranes that can be used. Some aspects of membrane operations, such as fouling, separation of a photocatalyst and effectiveness of photodegradation on permeate quality are discussed.

Electrical Resistivity Anisotropy of Silicon-Doped n-Indium Selenide

1993

The origin of slow electron recombination processes in dye-sensitized solar cells with alumina barrier coatings

2004

We investigate the effect of a thin alumina coating of nanocrystalline TiO2 films on recombination dynamics of dye-sensitized solar cells. Both coated and uncoated cells were measured by a combination of techniques: transient absorption spectroscopy, electrochemical impedance spectroscopy, and open-circuit voltage decay. It is found that the alumina barrier reduces the recombination of photoinjected electrons to both dye cations and the oxidized redox couple. It is proposed that this observed retardation can be attributed primarily to two effects: almost complete passivation of surface trap states in TiO2 that are able to inject electrons to acceptor species, and slowing down by a factor of…