Monte Carlo Simulation of Kinetic Phenomena in Solids Using OpenACC Parallel Computing Technology

Abstract

The development of a software package using the OpenACC parallel computing technology for Monte Carlo simulation of the kinetic coefficients of homogeneous semiconductor materials is presented. The package is a set of interconnected classes, the parameters of the material and external fields are redefined in the child classes available to the user, which makes it possible to model a wide range of materials. The package allows us to use models of elastic (acoustic phonons, charged impurities) and inelastic (polar and nonpolar optical phonons) electron scattering in the single-band approximation. The use of OpenACC technology makes it possible to use both shared memory systems and hybrid systems equipped with graphics processors as a computing platform. The possibility of saving data about each particle at each time step of the simulation is provided. It allowed, in particular, to trace the dependence of the average collision frequency of the energy of charge carriers and strength of the DC electric field applied to the sample, in the beta-modification of gallium oxide, to assess the applicability of the conductivity models offered by other research groups. It is shown that the greatest contribution to the conductivity of the beta modification of gallium oxide at room temperatures is made by the scattering of electrons on polar optical phonons, and the average collision frequency, as well as the percentage of collisions of an electron with various types of inhomogeneities of the crystal lattice, weakly depend on the strength of the constant electric field. At a temperature of about 100 K, with an increase in the constant electric field applied to the sample, firstly, the proportion of scattering with the emission of polar optical phonons increases significantly and the proportion of scattering on charged impurities decreases, and secondly, the total frequency of collisions increases. This is due, on the one hand, to the heating of the electron gas by an electric field and the activation of scattering channels with the emission of a phonon at a given temperature, on the other hand, to an insufficiently rapid increase in the concentration of current carriers due to the ionization of impurities. Thanks to the Monte Carlo simulation, it was possible to directly evaluate the validity of the use of the Farvaque correction for an approximate description of the processes of inelastic electron scattering on polar optical phonons by introducing some effective relaxation time.