Generation of III-Nitride Transport Parameters with Mocasim


Mocasim is an advanced three-valley Monte Carlo simulator designed to generate the transport parameters used in Silvaco’s physical device simulators. It accurately calculates the material transport parameters of both direct and indirect band gap semiconductors, including group IV and III-V material systems. With the recent interest in III-Nitride material systems, we have added the capability of simulating materials with wurtzite as well as zincblende and diamond lattices. Mocasim derives a multi-dimensional parameter set, including mobility, velocity, energy and momentum relaxation times, and inter-valley potential energy, all of which can be extracted as a function of applied electric field, doping density, mole fraction(s), and lattice temperature.

Mocasim is a physically based simulator. As such, it has three major advantages over empirical modeling:

It is predictive
It provides insight
It captures theoretical knowledge in a way that makes this knowledge easyto understand
Physically based simulation is different from empirical modeling. The goal of empirical modeling is to obtain analytic formulae that approximate existing data with good accuracy and minimum complexity. Empirical models provide efficient approximation and interpolation. They do not provide insight, predictive capabilities, or encapsulation of theoretical knowledge. Physically based simulation is an alternative to experiments as a source of data. Empirical modeling can provide compact representations of data from either source.

Physically based simulation has become important for two reasons: First, it is almost always much quicker and cheaper than performing experiments. Second, it provides information that is difficult, or impossible to measure. These advantages are of special interest in the case of III-Nitride materials, which can be difficult to manufacture and measure.

There are drawbacks as well to physically based simulation. The drawbacks are that all the relevant physics must be incorporated into the simulator, and numerical procedures must be implemented to solve the associated equations. These tasks have been taken care of for users of Mocasim. Physical scattering mechanisms built into Mocasim include scattering from polar and non-polar optical phonons, deformation potential acoustic phonons, piezo-electric acoustic phonons, ionized or neutral impurity scattering, and inter-valley phonon scattering.