Showing papers by "Enrico Bellotti published in 1998"

Monte Carlo study of electron initiated impact ionization in bulk zincblende and wurtzite phase ZnS

Abstract: This paper presents a theoretical study of the high field electronic transport properties of the cubic and hexagonal phases of zinc sulfide (ZnS) using an ensemble Monte Carlo method. Essential features of the model are the inclusion of realistic energy band structures calculated from a local pseudopotential method and numerically calculated impact ionization transition rates. The polar optical phonon scattering rate has also been computed numerically from the band structure. The relevant transport quantities have been computed for field values between 100 kV/cm and 2 MV/cm. On the basis of these calculations it is predicted that the electron distribution is cooler and the average energy lower in the wurtzite phase than in the zincblende phase over the entire field range examined. The difference in average energy between the two phases becomes pronounced for field magnitudes above 1 MV/cm while it is smaller in the field range between 700 kV/cm and 1 MV/cm. As a result, the ionization coefficients are exp...

Ensemble Monte Carlo Study of Electron Transport in Bulk Indium Nitride

Abstract: Ensemble Monte Carlo calculations of electron transport at high applied electric field strengths in bulk, wurtzite phase InN are presented. The calculations are performed using a full band Monte Carlo simulation that includes a pseudopotential band structure, all of the relevant phonon scattering agents, and numerically derived impact ionization transition rates. The full details of the first five conduction bands, which extend in energy to about 8 eV above the conduction band minimum, are included in the simulation. The electron initiated impact ionization coefficients and quantum yield are calculated using the full band Monte Carlo model. Comparison is made to previous calculations for bulk GaN and ZnS. It is found that owing to the narrower band gap in InN, a lower breakdown field exists than in either GaN or ZnS.

Monte Carlo Simulation of Hall Effect in n-Type GaN

Abstract: Results of Monte Carlo simulations of electron transport for wurtzite phase GaN in crossed, weak electric and magnetic fields are presented. It is found that the Hall factor, τ H = μ Hall /μ drift , decreases monotonically as the temperature increases from 77K to 400K. The low temperature value of the Hall factor increases significantly with increasing doping concentration. The Monte Carlo simulations take into account the electron-lattice interaction through polar optical phonon scattering, deformation potential acoustic phonon scattering (treated as an inelastic process), and piezoelectric acoustic phonon scattering. Impurity scattering due to ionized and neutral donors is also included, with the latter found to be important at low temperature due to the relatively large donor binding energy which implies considerable carrier freeze-out already at liquid nitrogen temperature. The temperature dependences of the electron concentration, drift mobility, and Hall factor are calculated for donor concentrations equal to 5 × 10 16 cm -3 , 10 17 cm -3 , and 5 × 10 17 cm -3 . The Monte Carlo simulations are compared to classical analytical results obtained using the relaxation-time approximation, which is found to be adequate at low temperatures and sufficiently low carrier concentrations so that inelastic scattering effects due to optical phonons and degeneracy effects are negligible. The influence of dislocations on the Hall factor is discussed briefly.