MAGNETIC AND ELECTRIC FIELD EFFECTS ON THE BINDING ENERGY OF A SHALLOW DONOR IN QUANTUM DOT–QUANTUM WELL

We studied the simultaneous of the magnetic and electric field effects on the binding energy for a shallow donor confined to move in spherical Quantum Dot – Quantum Well (GaAs-GaAlAs). Calculations are performed in the framework of the effective mass approximation using the Hass variational approach. We describe the effect of the quantum confinement by a infinite deep potential. The result shows that the corrections due to the magnetic and electric field are very important and cannot be neglected or ignored. We have demonstrated the existence of a critical value (a/b)cri which can be used to distinguish the three dimensions confinement from the spherical surface confinement and it’s may be important for the nanofabrication techniques.We studied the simultaneous of the magnetic and electric field effects on the binding energy for a shallow donor confined to move in spherical Quantum Dot – Quantum Well (GaAs-GaAlAs). Calculations are performed in the framework of the effective mass approximation using the Hass variational approach. We describe the effect of the quantum confinement by a infinite deep potential. The result shows that the corrections due to the magnetic and electric field are very important and cannot be neglected or ignored. We have demonstrated the existence of a critical value (a/b)cri which can be used to distinguish the three dimensions confinement from the spherical surface confinement and it’s may be important for the nanofabrication techniques

u/n-Si(100) contact homogeneity studied by direct and reverse ballistic electron emission microscopy and spectroscopy

The Au/n-Si(100) contact has been studied using reverse ballistic electron emission microscopy and spectroscopy. Two types of localised collector currents have been observed; one, positive corresponding to electron injection into Si, and the other, negative, associated with hole injection into the semiconductor. The comparative trial of BEEM and reverse BEEM images from the same area shows this difference to be linked to the interface structure. Effects of surface roughness on the observed contrasts are also discussed.The Au/n-Si(100) contact has been studied using reverse ballistic electron emission microscopy and spectroscopy. Two types of localised collector currents have been observed; one, positive corresponding to electron injection into Si, and the other, negative, associated with hole injection into the semiconductor. The comparative trial of BEEM and reverse BEEM images from the same area shows this difference to be linked to the interface structure. Effects of surface roughness on the observed contrasts are also discussed

Study of Au/n- ZnSe contact by ballistic electron emission microscopy

Ballistic Electron Emission Microscopy (BEEM) has been used to characterise the Au/n-ZnSe contact. A mean statistical BEEM threshold of 1.63eV is in good agreement with literature. Metal - Insulator- Semiconductor (MIS) structures are invoked to explain the Schottky barrier height dispersion and the observed shift of BEEM thresholds to higher values.Ballistic Electron Emission Microscopy (BEEM) has been used to characterise the Au/n-ZnSe contact. A mean statistical BEEM threshold of 1.63eV is in good agreement with literature. Metal - Insulator- Semiconductor (MIS) structures are invoked to explain the Schottky barrier height dispersion and the observed shift of BEEM thresholds to higher values

Binding Energy of Hydrogen-Like Impurities in Quantum Well Wires of InSb/GaAs in a Magnetic Field

The binding energy of a hydrogen-like impurity in a thin size-quantized wire of the InSb/GaAs semiconductors with Kane’s dispersion law in a magnetic fieldBparallel to the wire axis has been calculated as a function of the radius of the wire and magnitude ofB, using a variational approach. It is shown that when wire radius is less than the Bohr radius of the impurity, the nonparabolicity of dispersion law of charge carriers leads to a considerable increase of the binding energy in the magnetic field, as well as to a more rapid growth of binding energy with growth ofB

The Ground State Energy of a Bound Magneto-Polaron in Ternary Mixed Crystals

Theoretical calculations for the ground state energy of a bound magneto-polaron in the ternary mixed crystal A$_x$B$_{1-x}$C are presented. The theory is based on a variational approach using a trial wave function in the adiabatic limit. The electronic part of the wave function is the one used in the harmonic approximation. Numerical results are obtained for Ga$_x$Al$_{1-x}$As and show that the effect of phonons decreases on increasing the magnetic field and on decreasing the fraction $x$ of the compounds

Section efficace de photoionisation dans les semiconducteurs Polaires

Theoretical expression for the photoionization cross section of semi-deep level impurity is developed as a function of photon energy. In this model we take account to the interaction between the charge carriers and the longitudinal optical phonons of polar semiconductors and the influence of central-cell correction by means of a semi-empirical short range potential. The results obtained are compared with reported experimental and theoretical results.Des expressions théoriques de la section efficace de photoionisation sont developpées pour les états d'impuretés semi-profonds en fonction de l'énergie du photon. Dans ce modèle, nous tenons compte de l'interaction porteur de charge-phonon ainsi que de la correction de cellule centrale par le moyen d'un modèle analytique du potentiel de l'impureté. Les résultats obtenus sont comparés avec les données expérimentales et théoriques

Study of Au/n- ZnSe contact by ballistic electron emission microscopy

Ballistic Electron Emission Microscopy (BEEM) has been used to characterise the Au/n-ZnSe contact. A mean statistical BEEM threshold of 1.63eV is in good agreement with literature. Metal- Insulator- Semiconductor (MIS) structures are invoked to explain the Schottky barrier height dispersion and the observed shift of BEEM thresholds to higher values. PACS: 73.30.+y, 61.16.ch, 73.23.Ad, 73.61.Ga I

Au/n-Si(100) contact homogeneity studied by direct and reverse ballistic electron emission microscopy and spectroscopy

The Au/n-Si(100) contact has been studied using reverse ballistic electron emission microscopy and spectroscopy. Two types of localised collector currents have been observed; one, positive corresponding to electron injection into Si, and the other, negative, associated with hole injection into the semiconductor. The comparative trial of BEEM and reverse BEEM images from the same area shows this difference to be linked to the interface structure. Effects of surface roughness on the observed contrasts are also discussed. PACS: 61.16P, 73.40N, 68.20 I

Optical Absorption Coefficient on-center donor impurity in a spherical core/shell quantum dots

The polaronic effect on the linear, third-order nonlinear and total optical absorption coefficients have been calculated in the case of GaAs/AlAs core/shell quantum dot, with the impurity is positioned at the central radial position of the GaAs shell. The calculations are realized in the framework of the effective mass approximation and the numerical results are obtained by using a variational method and an infinite confining potential. The results show that the polaronic effect has a great influence on optical properties of core/ shell quantum dot, he causes a red-shift of the nonlinear optical coefficients associated to light absorption. Also, the polaronic effect is enhanced with the decreasing of quantum dot radius