Peter A. Blakey

Simulation of GaAs IMPATT diodes including energy and velocity transport equations

Simulations have been performed of GaAs hybrid double-drift IMPATT diodes at 60 and 94 GHz using a transport model which includes equations for the average per-carrier velocity and energy. These equations are obtained from the second and third velocity moments of the Boltzmann transport equations, respectively. The relaxation-time formulation is used to characterize the collision terms. Simulations were also carried out for the same structures using the standard drift-diffusion transport model. It was found that inclusion of the energy-velocity equations significantly modifies the predicted carrier transport behavior and results in somewhat better RF performance under large-signal conditions than that predicted by the drift-diffusion simulation.

Large-signal time-domain modeling of avalanche diodes

Large-signal, time-domain modeling (simulation) of avalanche diodes is potentially a very accurate and useful tool for the study and design of these devices. Unfortunately, difficult computational problems of stability, accuracy, and efficiency can easily interfere with the production of meaningful, cost-effective results. This paper identifies the problems commonly encountered, including poor accuracy of the avalanche generation description; numerically induced pseudodiffusion; modeling of unsaturated velocity and negative mobility carrier dynamics; field reversal; and the treatment of the diode-load interaction, and describes numerical methods developed to overcome them. The methods described are believed to represent a current state-of-the-art efficiency/accuracy compromise for avalanche-diode simulation.

Effects of transient carrier transport in millimeter-wave GaAs diodes

Effects of transient carrier transport on the performance of millimeter-wave GaAs diodes are investigated using results obtained from a Monte Carlo simulation of electron transport. Transit-time devices (such as IMPATTs and TUNNETTs) are discussed first. Mechanisms by which transient effects in the drifting charge pulse may enhance or degrade performance are identified and discussed. Attention is then focused on electron transport in the undepleted epitaxial material which will be present in mixer and varactor diodes and may be present in transit-time diodes. The frequency and signal-level dependence of the conductance of such material is calculated and the implications for device performance are discussed.

Self-Consistent Particle-Field Monte Carlo Simulation of Semiconductor Microstructures

A recently developed self-consistent particle-field Monte Carlo simulation is described and results obtained using it are presented. The implementation is applicable to unipolar (electronic) devices fabricated from GaAs and InP. The first part of the paper outlines the different algorithms used for scalar (conventional) and vector (supercomputer) processors, and presents representative timing and cost data in various forms. The importance of boundary conditions is emphasized.

The impact of three-dimensional effects on EEPROM cell performance

Device simulation is used to investigate three-dimensional effects in small electrically erasable programmable read-only memory (EEPROM) cells. Threshold voltage, tunnel currents, write speed, and the effects of misregistration are characterized for a structurally parameterized generic FLOTOX EEPROM cell. The results indicate considerable sensitivity to three-dimensional effects. Design insights for small EEPROM cells are discussed. >

Comments on "Effects of carrier diffusion on the small-signal behavior of IMPATT diodes"

The above paper presented computed results for the effects of carrier diffusion on the small-signal behavior of avalanche diodes. It is suggested that these results be treated with caution, since the equations solved are not those normally associated with the problems under consideration. Other aspects of the paper1which could be misleading are also indicated.

The Influence of Contacts on the Behavior of Near and Sub-Micron InP Devices

We discuss the status of the preliminary results of: 1) numerical calculations of submicron (≦ 0.5 μm) two-terminal InP N+ -N-N+ transferred electron devices; 2) experiments on near micron InP (≧ 1.0 μm) devices. Our calculations used both Monte Carlo techniques and a static velocity-field parameter model. Contact and interface effects were emphasized. Besides obtaining known, well-documented results such as the effect of Debye tail diffusion, we also found that the anode contact region can become important in short device structures. Experimentally, we have observed both conventional and unconventional behavior, such as the existence of anomalous modes of amplification.