Narrow Results

A simplified model of electron transport by tunneling within a GaAs/AlGaAs/GaAs heterojunction is developed. The model is applied specifically to tunneling through a triangular barrier formed by the compositional grading of the AlGaAs region, but can in principle be extended to a range of barrier geometries encountered at heterojunction or metal/semiconductor interfaces. The experimental data for the current-voltage characteristics obtained for a range of temperatures from 77 K to 273 K are used to test the functional dependence obtained from calculations. Good agreement has been obtained between theory and experiment, thus confirming the usefulness of the simple model for device evaluation.

Numerical simulations are performed for SiGeC/Si electrooptic modulators and photodetectors operating at near-IR wavelengths. The addition of carbon provides the ability to lattice match layers with high germanium composition to silicon, which is shown to allow structures with a substantial increase in the optical confinement factor. In addition, SiGeC/Si heterostructures provide strong confinement of large electron and hole concentrations. The large optical confinement factor and strong carrier confinement enable broadband electrooptic modulators with sub-100 μm lengths and switching times below 0.5 ns with 25 mA current as well as photodetectors with quantum efficiencies as high as 90% for 300 μm length.

In this paper, an efficient numerical model applicable for wide varieties of long channel field-effect transistors (MOSFET, MESFET, HEMT, etc.) is developed. A set of available data is used to calculate the model parameters and another set of data is used to verify the accuracy of the model. This model provides a single expression that is applicable for the entire range of device biasing and can predict the output parameters with less than 1% error compared to the experimental results. Lagrange polynomial, the highest degree of polynomial for any given set of data, is used to derive the model from available data. This method is efficient in the sense that it can be derived from a limited number of experimental data and since it uses only one equation for entire range of the device operation hence its computational cost is also small.

Various physics based modeling schemes for multigate MOSFETs are presented. In all cases, the models are derived from an analysis of the device body electrostatics in terms of two- or three-dimensional Laplace's and Poisson's equations, where short-channel and scaling effects are implicitly accounted for. Thus a comprehensive modeling framework is derived for the subthreshold electrostatics of double-gate MOSFETs based on a conformal mapping analysis of the potential distribution in the device body arising from the inter-electrode capacitive coupling. This technique is also applied to the circular gate-all-around MOSFET by utilizing the symmetry properties of this device. For both these devices, the modeling is extended to include the strong inversion regime by a self-consistent procedure that simultaneously allows the calculation of the quasi-Fermi potential distribution, the drain current, and the intrinsic capacitances. In an alternative modeling framework, covering a wide range of multigate devices in a unified manner, the potential distribution is derived from a select set of isomorphic trial functions that reflect the geometry and symmetry properties of the devices. Modeling parameters used are self-consistently determined by imposing boundary conditions associated with Laplace's or Poisson's equation. Finally, the effects of quantum mechanical confinement are discussed for ultra thin body devices. The results of the modeling are in excellent agreement with numerical simulations.

This paper presents particle swarm optimization (PSO) method to solve the parameter estimation problem of the Schottky-barrier diode model. Based on the synthetic and experimental data, we have demonstrated that the proposed method has high parameter estimation accuracy. Besides, the initial guesses for the model parameter values are not required in the PSO method. Also, the performance of the PSO method is compared with that of the genetic algorithm (GA) method. The results indicate that the PSO method outperforms the binary-coded and real-coded GA methods in terms of estimation accuracy and computation efficiency.

An ensemble Monte Carlo simulation has been used to model bulk electron transport at room and higher temperatures as a function of high electric fields. Electronic states within the conduction band valleys at the Γ₁, U, M, Γ₃ and K are represented by non-parabolic ellipsoidal valleys centred on important symmetry points of the Brillouin zone. The simulation shows that intervalley electron transfer plays a dominant role in GaN in high electric fields leading to a strongly inverted electron distribution and to a large negative differential conductance. Our simulation results have also shown that the electron velocity in GaN is less sensitive to temperature than in other III-V semiconductors like GaAs. So GaN devices are expected to be more tolerant to self-heating and high ambient temperature device modeling. Our steady state velocity-field characteristics are in fair agreement with other recent calculations.

A simplified model of electron transport by tunneling within a GaAs/AlGaAs/GaAs heterojunction is developed. The model is applied specifically to tunneling through a triangular barrier formed by the compositional grading of the AlGaAs region, but can in principle be extended to a range of barrier geometries encountered at heterojunction or metal/semiconductor interfaces. The experimental data for the current-voltage characteristics obtained for a range of temperatures from 77 K to 273 K are used to test the functional dependence obtained from calculations. Good agreement has been obtained between theory and experiment, thus confirming the usefulness of the simple model for device evaluation.

Numerical simulations are performed for SiGeC/Si electrooptic modulators and photodetectors operating at near-IR wavelengths. The addition of carbon provides the ability to lattice match layers with high germanium composition to silicon, which is shown to allow structures with a substantial increase in the optical confinement factor. In addition, SiGeC/Si heterostructures provide strong confinement of large electron and hole concentrations. The large optical confinement factor and strong carrier confinement enable broadband electrooptic modulators with sub-100 μm lengths and switching times below 0.5 ns with 25 mA current as well as photodetectors with quantum efficiencies as high as 90% for 300 μm length.

In this paper, an efficient numerical model applicable for wide varieties of long channel field-effect transistors (MOSFET, MESFET, HEMT, etc.) is developed. A set of available data is used to calculate the model parameters and another set of data is used to verify the accuracy of the model. This model provides a single expression that is applicable for the entire range of device biasing and can predict the output parameters with less than 1% error compared to the experimental results. Lagrange polynomial, the highest degree of polynomial for any given set of data, is used to derive the model from available data. This method is efficient in the sense that it can be derived from a limited number of experimental data and since it uses only one equation for entire range of the device operation hence its computational cost is also small.

Various physics based modeling schemes for multigate MOSFETs are presented. In all cases, the models are derived from an analysis of the device body electrostatics in terms of two- or three- dimensional Laplace's and Poisson's equations, where short-channel and scaling effects are implicitly accounted for. Thus a comprehensive modeling framework is derived for the subthreshold electrostatics of double-gate MOSFETs based on a conformal mapping analysis of the potential distribution in the device body arising from the inter-electrode capacitive coupling. This technique is also applied to the circular gate-all-around MOSFET by utilizing the symmetry properties of this device. For both these devices, the modeling is extended to include the strong inversion regime by a self-consistent procedure that simultaneously allows the calculation of the quasi-Fermi potential distribution, the drain current, and the intrinsic capacitances. In an alternative modeling framework, covering a wide range of multigate devices in a unified manner, the potential distribution is derived from a select set of isomorphic trial functions that reflect the geometry and symmetry properties of the devices. Modeling parameters used are self-consistently determined by imposing boundary conditions associated with Laplace's or Poisson's equation. Finally, the effects of quantum mechanical confinement are discussed for ultra thin body devices. The results of the modeling are in excellent agreement with numerical simulations.