Impact Ionization Probability Research Articles

Transition probability of impact ionization in silicon

Transition probability of impact ionization in silicon

Role of Carrier Polarization in the Mechanism of the Electroluminescence of ZnSMn Films

AbstractA polarization which remains constant over a period of time and is caused by the accumulation of carriers in deep surface traps is observed in EL ZnSMn films. The polarization characteristics (i.e., the number of polarization charges, the time‐dependence of its formation and destruction, the ionization energy of the traps, etc.) are determined in order to study the role of carrier polarization in the mechanism of EL. It is established that the polarization mainly affects the change in the internal field and therefore the impact ionization probability. Also, at the instant of voltage‐polarity reversal, the polarization charge ionization leads to an increase in the number of carriers which can accelerate. All the EL properties and features of ZnSMn films may be explained on the basis of an impactionization mechanism if the polarization effects are taken into account.

Transition probability of impact ionization in silicon

Using time dependent perturbation calculation and Bloch functions for the states of electrons and the hole, transition probability per unit time for electron-hole pair generation by impact ionization has been obtained. Further, utilizing the various possibilities in the types of momenta conservation with energy conservation relation, it is shown that there are several thresholds of energy. Three of these are found taking band structure of silicon in (1, 0, 0) direction. The total probability per unit time of pair generation by impact ionization has been estimated for energies lying between the lowest and the next higher threshold of ionization. It is found that the probability of ionization increases with increasing energy of the ionizing electron.

Impact Ionization of Centers in Solids by Electrons Accelerated by an Electric Field

AbstractThe probability of impact ionization of centers by electrons which have been accelerated in an electric field is calculated using time dependent perturbation theory. The wave function for a bound electron is taken to be of the form Ψ = (λ3/π)1/2 exp (‐ λr) and the effective mass approximation is used for the band. A modified Boltzmann function is used for the electrons in the band, and it is shown that impact ionization can only be important, in high resistivity materials, if the electric field is high even to raise the electron temperature well above lattice temperature. The effect on the current‐voltage characteristic is examinated for two simple cases and it is found that a steep rise due to impact ionization can occur. Electrons trapped in neutral centres are somewhat more important than electrons in negative centres, whilst electrons in positive centres are very much less important. It is also shown that the effect of impact ionization will, in general, only be important if most of the electrons which are released are trapped in other shallow traps.