COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering

Banghart, Edmund K.; Lavine, James P.; Pimbley, Joseph M.; Burkey, Bruce C.

1991 COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering

doi: 10.1108/eb051699

Numerical and analytical solutions of the carrier continuity equation are found for the problem of charge transfer in chargecoupled devices in the presence of potential barriers. The analytical solution is for a rectangular potential barrier and is useful for obtaining a qualitative understanding of charge transfer over a potential barrier. Numerical results show that the charge transfer inefficiency is strongly affected when the shape of the potential barrier is varied and the height of the potential barrier remains fixed.

Efrat, Ilan; Israeli, Moshe

1991 COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering

doi: 10.1108/eb051700

State of the art programs for the solution of the drift diffusion semiconductor equations are based on finite difference techniques, or on certain combinations of finite elements and finite differences. The extreme gradients which occur in semiconductor devices have motivated several attempts to exploit perturbation analysis in order to improve the numerical scheme. Selberherr, Markowich et. al. showed the singular perturbation nature of the drift diffusion equations. Their analytic approximations of diodes influenced some aspects of the Minimos and Bambi simulators. Asymptotic analyses of MOSFET were presented by Brews and by Ward. These solutions are mainly valid for long channels, and their accuracy is limited.

MICHEZ, A.; BORDURE, G.

1991 COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering

doi: 10.1108/eb051701

This paper presents an approach to the time discretization of electron and hole continuity equations in semiconductors. We propose a nth order backward differentiation formula with variable stepsize determined by a local truncation error evaluation. Up to the fifth order is examined. As an example, the effect of a heavy ion 63Cu , 70 MeV on a silicon diode is simulated with a 3D axisymmetrical model, using various time stepping schemes. The results obtained are compared. For this particular problem and the mesh considered, the third order is the most efficient one to reduce the calculation time.

Buot, F.A.; Jensen, K.L.

1991 COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering

doi: 10.1108/eb051702

Intrinsic highfrequency oscillations 2.5 THz in current and corresponding quantum well density, which have been simulated for a fixed bias voltage in the Negative Differential Resistance NDR region of the CurrentVoltage IV characteristics of a Resonant Tunneling Diode RTD, suggest an equivalent nonlinear autonomous circuit model. The intrinsic circuit parameters are calculated directly from the results of the quantum transport numerical simulations. These consist of a resistor in series with a twobranch parallel circuit, one branch consists of a capacitor and the other branch consists of an inductor in series with a nonlinear resistor. It is however suggested that much more complex external circuitinduced behavior can occur in real RTD experiments.

Li, Z.M.; Dzurko, K.M.; McAlister, S.P.

1991 COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering

doi: 10.1108/eb051703

We have developed a twodimensional model for quantumwell lasers which solves, selfconsistently, the semiconductor equations together with the complex scalar wave equation and the photon rate equation. To predict the threshold current accurately we have included the wavelength and positiondependence of the gain and the spontaneous emission. For the complex wave equation successive over relaxation SOR is used with two adaptive acceleration parameters for the complex wave amplitude and for the eigenvalue. Since the rate equation near threshold can be driven into divergence during iteration for a steady state solution, we have introduced a special damping technique to overcome this problem. Our model enables us to predict the characteristics of a quantumwell laser with a minimal number of empirical constants. The output of the model includes lightcurrent characteristics, and the current and optical field intensity distributions. We show the results of a calculation for a gradedindex separateconfinement heterostructure single quantumwell GRINSCH SQW laser.

Anwar, A.F.M.; Carrol, R.D.

1991 COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering

doi: 10.1108/eb051704

The effect of doping the quantum well QW on the distribution of two dimensional electron gas 2DEG in high electron mobility transistors HEMT is discussed. In conventional HEMTs the QW is unintentionally doped to utilize the higher mobility of the QW material. The overlap between the carrier and the dopant distribution may be minimized by selectively doping the QW.

Cheng, MingCheng; Kunhardt, E.E.

1991 COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering

doi: 10.1108/eb051705

A nonequilibrium multivalley transport model for carriers in compound semiconductor devices has been developed. This macroscopic transport model provides an efficient scheme for device modeling, and can overcome the difficulty in evaluating the relaxation times in multivalley conservation equations without a priori assumption of the displacedMaxwellian distribution. This model has been successfully applied to electron transport in GaAs subjected to rapidly timevarying fields. The results have suggested that the macroscopic effective mass of electrons might be strongly dependent on average velocity.

Hamza, Mohammad; Morel, H.; Chante, J.P.

1991 COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering

doi: 10.1108/eb051706

A full consistent discretization scheme of the improved carrier density, momentum and energyconservation equations is presented. The carrier heat flux as well as the convection and recombination terms are considered. The convection terms are averaged and then the differential constitutive relations of the current density and the energy flux are solved. The proposed discretization scheme generalizes the ScharfetterGummel SG difference approximation to the generalized hydrodynamic model HDM. On the basis of this scheme the hydrodynamic equations HDE's are solved for both electrons and holes. The transport of hot carriers in the pin diode is investigated over a large scale of biasing values. The electric field distribution is not severely purturbed by the hot electron effects up to the medium biasing range. However, the minority carrier distribution is significantly affected by the carrier temperaturegradients near the spacechargeregions. The minority carriers that are diffused to the edge of depleted regions are heated and if the carrier temperature gradient is sufficiently strong they diffuse back to the neutral cold region rather than to be captured by the electric field as known from the standard DDM theory.

Teeter, Douglas A.; East, Jack R.; Mains, Richard K.; Haddad, George I.

1991 COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering

doi: 10.1108/eb051707

This model is intended to simulate the large signal performance of heterojunction bipolar transistors for use in high power, high frequency, oscillators, amplifiers, and mixers. A temperature model which includes velocity overshoot and carrier energy effects has been developed. The model is used to calculate the large signal Y parameters of an HBT. A comparison is made between predicted power performance using the Y parameters and a fully numerical, time domain computation. Advantages and disadvantages of each approach are given.

Wachutka, Gerhard

1991 COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering

doi: 10.1108/eb051708

The thermodynamic model constitutes a unified theoretical framework for the coupled simulation of carrier and energy flow in semiconductor devices under general ambient conditions such as, e.g., the presence of a quasistatic magnetic field or the interaction with an electromagnetic radiation field light. The current relations governing particle and heat transport are derived from the principles of irreversible phenomenological thermodynamics the driving forces include drift, diffusion, thermal diffusion, and deflection by the Lorentz force. All transport coefficients may be interpreted in terms of wellknown thermodynamic effects and, hence, can be obtained from theoretical calculations as well as directly from experimental data. The thermodynamic model allows the consistent treatment of a wide variety of physical phenomena which are relevant for both the operation of electronic devices e.g., lattice heating, hot carrier and low temperature effects and the function of microsensors and actuators e.g., thermoelectricity, galvanomagnetism and thermomagnetism.