A general-purpose, self-consistent ensemble Monte Carlo model is developed for probing high-field transport and ultrafast phenomena in compound semiconductor devices. The model includes a "superparticle model" with "cloud-in-cell" charge assignment scheme for either separate or combined background electron and photogenerated carrier sub-ensembles, which couples the Poisson solver to the Monte Carlo algorithm using the evolving distribution functions in a self-consistent way. The program employs an "adaptive" energy scale in combination with the well-known "piece-wise constant G" and the "fast self-scattering" techniques for the self-scattering approximation, which reduces the self-scattering rate while maintaining the resolution of the energy distribution histogram without assuming a priori the electron maximum energy.

The band structure used is a three-valley (G-L-X) conduction band including nonparabolicity for any III-V ternary compound material (default is AlGaAs) with position-dependent alloy composition. It assumes a flat valence band (infinitely large hole effective masses) when photogenerated electron–hole pairs are injected, and the holes are assumed to be immobile. Arbitrary material composition, impurity profile, and applied voltage/field can be specified. Scattering mechanisms included are intervalley and intravalley phonon scatterings, polar optical phonon scattering (with either screened or unscreened electron–phonon interaction via a self-consistent screening model), acoustic phonon scattering, ionized impurity scattering, and electron–electron scattering, which can be turned on or off separately.

A variety of initial and boundary conditions can be specified to facilitate the analysis of carrier transport and relaxation processes in semiconductor devices. The current model is applicable to devices of one-dimensional in nature, such as bulk materials, bipolar-type devices, heterostructure hot-electron diodes/transistors, photocarrier transport and relaxation processes, etc. The model has been applied, for the first time, to study photocarrier transport in GaAs surface space-charge fields and femtosecond dynamics of hot-carrier relaxation and scattering processes in bulk GaAs. These studies have detailed the dynamics of carrier transport and provided physical insights into the phenomena in the experimental measurement context. The simulation results are in good qualitative agreement with experimental observations, and further demonstrate the power of the Monte Carlo approach to modeling these high-field and ultrafast transport processes.

UMI Dissertation Information Service: Order Number: 9111520

(See also: EE-90-09)