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GaN-based pseudomorphic heterostructures with their demonstrated superior thermal performance suggest an alternative to the standard GaAs-based technology to realize high power lasing at THz frequencies. A larger electron effective mass in GaN based system results in the energy levels lying deeper within the quantum well compared to its GaAs counterpart resulting in longer carrier lifetimes assisting transitions required for THz radiation while reducing tunneling current. However, the presence of spontaneous and piezoelectric polarization and dependence of bandgap and band offsets on structural and bias induced strain reduces carrier lifetime.

Alternative channel materials with superior transport properties over conventional silicon based systems are required for supply voltage scaling in CMOS circuits. Group III-Sb's are a candidate for high mobility p-channel applications due to a low hole effective mass, large injection velocity in scaled devices and the ability to achieve enhanced hole mobility in strained quantum wells (QW). Multiple challenges in antimonide MOSFET development are assessed and developed technologies were implemented into p-channel MOSFET fabrication with a low thermal processing budget of 350°C. These challenges include growth of “bulk” GaSb and bi-axial compressively strained In_xGa_1-xSb QW channels on lattice mismatched GaAs substrates, reduction of interface trap state density (D_it) at the III-Sb/high-k oxide interface and avoiding ion implanted source and drain contacts with high temperature activation annealing. A “self-aligned” single mask p-channel MOSFET fabrication process was developed on buried In_0.36Ga_0.64Sb QW channels using intermetallic source and drain contacts. The first “gate-last” MOSFET process on In_0.36Ga_0.64Sb QW channels with pre-grown epitaxial p⁺⁺-GaSb contacts is demonstrated. InAs has been proven to be an excellent etch stop layer when using an optimized tetramethylammonium hydroxide (TMAH) etch of p⁺⁺-GaSb to prevent InGaSb QW damage.

A novel approach for cascade diode lasers was developed based on type-I quantum wells (QWs). This design adopted the leaky window effect in the GaSb/InAs band alignment for cascade pumping, and exploits the carriers recycling by the cascade pumping and the high optical gain of the type-I QWs. Two-stage cascade lasers were designed and fabricated for 2.45 and 3.0 μm, demonstrating twofold improvement in the internal efficiency. Record continuous-wave (CW) output power of 1.2 W for 2.45 um and 590 mW for 3.0 um were achieved in room temperature (RT), and the devices operate with higher power conversion efficiency at high power level, compared to conventional single-stage diode lasers.

In this work we calculate and analyze modal gain for terahertz lasers based on HgCdTe heterostructures with quantum wells (QWs) taking into account the symmetry-enforced light hole-heavy hole mixing at the quantum well interfaces. We have found that modal gain for a structure with 5 HgTe QWs of the 5.2 nm width can be 33 cm⁻¹ at 9 THz.

In this paper, novel features offered by Resonant Tunneling Diode (RTD) are reviewed by simulating it under different conditions. GaAs/AlGaAs based RTD is used as the reference one to obtain the characteristics due to parametric variations. To fulfil this purpose a simple model of resonant electronic transport through a double-barrier structure is developed. I-V characteristics are studied by varying barrier parameters and well width. Different peak and valley currents are measured under these conditions. For the same set of parameters both symmetric and asymmetric cases are considered. Different materials of lower effective mass are also taken into consideration to improve Peak to Valley Ratio (PVR). The Indium (In) based materials are considered to compare the characteristics obtained from the conventional GaAs based RTD structure. All these proposed structures are simulated using Silvaco Atlas software.

We applied the mosaic crystal model to calculate the dynamical x-ray rocking curves for a coherently-strained GaAs/In_0.3Ga_0.7As/GaAs single quantum well grown epitaxially on a GaAs (001) substrate for a number of reflection profiles, including 004, 113, 224, 044 and 444 reflections. We show that it is possible to estimate the threading dislocation density in the quantum well, and therefore detect the pseudomorphic-metamorphic transition, using the widths or normalized intensities of the primary quantum well Bragg peak, or using the widths of the Pendellösung fringes associated with the quantum well structure.

This paper presents the design and modeling of AND/OR logic gate using one high-mobility n-channel spatial wave-function switched field-effect transistor (n-SWS-FET), which provide a significant reduction of cell area and power dissipation. In SWSFET, the channel between source and drain has two or more quantum well (QW) layers separated by a high band gap material between them. The gate voltage controls the charge carrier concentration in the two quantum well layers and it causes the switching of charge carriers from one channel to other channel of the SWS device. This switching property promises to build AND/OR logic gate with one n-SWS-FET transistor, where Complementary Metal Oxide Semiconductor (CMOS) AND/OR gate is built by 6 transistors. The proposed gate configures as AND/OR by change sources signal. The SWS-FET device with two well Si/Si_0.5Ge_0.5 has been modeled using Berkeley Short-channel IGFET Model (BSIM4.6.0) and Analog Behavioral Model (ABM), the model is suitable for transient analysis at circuit level. This model is optimized for AND/OR logic and used to replace a conventional CMOS logic.

The binding energy of a shallow acceptor in an isolated quantum well of the CdTe/Cd_1-xMn_xTe system has been investigated in an external magnetic field, assuming an empirical relationship between the barrier height and the magnetic field. Photoionization cross-sections for different magnetic fields have been estimated. Taking into account the confined phonons in the electron-phonon interaction, carrier capture times for various magnetic fields and different hydrostatic pressures have been computed. The results obtained are discussed in the light of the existing literature.

The temperature dependent binding energy of some low lying excited states for a compositional Quantum Well have been calculated for various impurity locations by extending the investigation of Elabsy.⁴ It has been observed that the temperature plays an important role in the binding energy of low lying excited states also.

We show, from self-consistent calculations, that the effective mass for motion of holes along a two-dimensional (111) Ge layer is almost an order of magnitude smaller than the bulk heavy hole mass, which determines the intersubband distances. This creates a unique situation of multiple populated electric subbands at moderate hole densities p_s and layer widths. Depopulation of two or more upper subbands in a 38 nm wide p-Ge layer with p_s=5×10¹⁵m^-2 has been revealed from the magnetoresistance in high parallel magnetic fields, while a collapse of the quantum Hall state for filling factor ν=1 indicates that two ground subbands merge in a self-formed double-quantum-well potential profile. The latter effect in the valence band is shown to be sensitive to the layer deformation.

We present a complete Monte Carlo simulation of the transport properties of a Si/SiGe quantum well. The scattering mechanisms, viz. intervalley phonons, acoustic phonons, interface roughness and impurity scattering (including resonant scattering), are considered in detail, and we derive analytic expressions for the scattering rates, in each case properly taking the quantized electron wave functions into account. The numerically obtained distribution function is used to discuss the influence of each scattering mechanism for different electric fields applied parallel to the interfaces and also different temperatures.

The effect of Γ-X crossover due to the external hydrostatic pressure on the ground state donor binding energy as well as for some low lying excited states for a Quantum well has been investigated by considering the non-parabolicity of the conduction band and pressure dependent spatial dielectric screening. It is observed that the effect of Γ-X crossover is predominant for ground state than for low lying excited states.

We study by the variational method the effects of external magnetic field on the interface exciton with a hole confined in the quantum well. The main parameters of our model are: the distance d between the interface plane and center of the quantum well, the parameters of quantum well (the half width a and the height V₀) and magnetic length λ. We obtained the binding energy and effective optical efficiency of this type of interface exciton. This model can be developed to investigate the properties of two-dimensional excitons in coupled quantum well.¹

The binding energies of excitons in finite barrier quantum wells under hydrostatic pressure are calculated by a variational method. The influences of hydrostatic pressure on the effective masses of the electron and hole, the dielectric constant, and the conduction band offset between the well and barriers are taken into account in the calculation. The numerical results for the GaAs/Al_xGa_1-xAs and GaN/Al_xGa_1-xN quantum wells are given respectively. It is shown that the exciton binding energy increases linearly with the pressure and the pressure effect on arsenide quantum wells is more obvious than that on nitride ones. The exciton binding energies monotonically increase with increasing barrier height, which is related to the Al concentration of the barriers and the influence of the pressure.

The effect of spatial dielectric screening on the diamagnetic susceptibility (χ_dia) of a donor in Low Dimensional Semiconducting Systems like Quantum Well, Quantum Well Wire and Quantum Dot in the infinite barrier model has been computed and investigated within the effective mass theory using variational method. We observe that the effect of spatial dielectric screening on χ_dia decreases with decrease of dimensionality of the system.

Quasi-two-dimensional structures are characterized by multiple sub-bands and depending upon the well width and electron density, several sub-bands may be occupied. With an increase in well width more sub-bands are pushed below the Fermi level leading to a possible nonmonotonic variation in transport coefficients. This paper investigates Seebeck coefficient and Lorenz factor in Si_0.9Ge_0.1 quantum wells taking into account the multiple sub-band contributions.

The influences of the temperature and the phonons effect on the properties of the exciton, which is strongly coupled with interface optical (IO) phonons and weakly coupled with bulk longitudinal-optical (LO) phonons, in a quantum well are studied by means of Huybrechts' linear-combination operator and the Lee–Low–Pines variational method. The expressions for the induced potential of the ground state, the energy shift of the ground state, and the first internal excited state of the exciton were derived. Numerical results are illustrated for AgBr/AgCl quantum well. The results indicate that the induced potential of the ground state, the energy shift of the ground state, and the energy shift of the first internal excited state of the exciton produced by the exciton strongly coupling with IO phonons increase with increasing temperature; however, the induced potential of the ground state, the energy shift of ground state, and the energy shift of the first internal excited state of the exciton produced by the exciton weakly coupling with bulk LO phonons decrease with increasing temperature. The influence of temperature is greater to the changes of the induced potential and the energy shift of the exciton with well widths and the distances between electron and hole.

The effect of laser on the nonparabolicity of the conduction band for hydrogenic donor states like 1s, 2s, 2p_± and 2p₀ in a GaAs/Al_xGa_1-xAs quantum well have been computed in a finite barrier model using variational principle in the effective mass approximation. The limiting values of the ground state and few excited state binding energies for a laser dressed-donor have been obtained. The results are presented and discussed.

In this work, we have studied some computational aspects of a Monte Carlo method applied to an exciton which is confined in an AlGaAs/GaAs single quantum well. The computational pseudo-code and effect of its computational parameters like number of the Monte Carlo sampling points on a physical quantity like exciton binding energy are investigated. Then the CPU time under the change of such computational parameters are calculated. Finally, the exciton binding energy and errors of different methods of approximating the effective two dimensional coulomb potential for these systems are compared.

Magnetic induction dependence of the dispersion of longitudinal magnetoplasmon in a two-dimensional electron gas with finite layer thickness under a static uniform magnetic field normal to the layer plane is calculated using the self-consistent linear response approximation. Two longitudinal magnetoplasmon modes are obtained. The calculated dispersion agrees with the experiment by Batke et al. [Phys. Rev. B34, 6951 (1986)].