Threshold Energy For Impact Ionization Research Articles

Hot phonon effects on impact ionization dynamics in InSb

A novel ensemble Monte Carlo technique is applied for the study of interband impact ionization dynamics in InSb under the nonequilibrium phonon conditions. It is shown that hot phonons reduce the impact ionization threshold field and considerably increase the electron-hole generation rate at near-threshold fields. The time during which the electrons reach the impact ionization threshold energies is reduced by hot phonons.

Light emission from the GaAs/AlGaAs HBT collector junction at breakdown

The authors report the observation of light emission from the GaAs collector-base junction of a GaAs/AlGaAs HBT (heterojunction bipolar transistor) at breakdown. The photoemission spectra of the reverse-bias junction and resolved peaks at 2.03 and 1.43 eV were measured, with the intensities dependent upon the reverse current. An experimental technique for measuring the threshold energy for impact ionization in the investigated material is reported.

Theory of steady-state high-field hole transport in GaSb and AlxGa1−xSb: The impact ionization resonance

Calculations of the steady-state impact ionization rate of holes in GaSb and AlGaSb are presented based on a Monte Carlo simulation with the unique inclusion of a complete band structure (derived using the K*P method) and quantum effects such as initial state collision broadening. It is determined, by comparisons to existing experimental data, that the holes in the split-off band play the most important role in impact ionization in both GaSb and GaAlSb. The experimental data are fit quite well at low applied electric fields where the recently discovered resonance in the hole impact ionization rate occurs. It is found that the resonance data can be explained, using the parametrized Keldysh formula, if the impact ionization threshold energy in both the heavy- and light-hole bands is ∼1.40 eV, roughly twice the band-gap energy, The threshold energy in the split-off bands is taken to be equal to the split-off energy for Δ>

On the properties of InSb quantum wells

A brief survey of the properties of InSb quantum wells is reported. The energy level scheme is described on the basis of a square-well model taking into account the pronounced non-parabolicity of the conduction band. A simple model for electron transport with polar optical mode scattering is presented. The temperature dependence of the low-field electron mobility is calculated for various well-widths. Threshold fields for negative differential resistance and for energy runaway are estimated. Threshold energies for impact ionization, including resonance effects involving the electronic sub-bands are also obtained. Novel features expected of InSb quantum wells are summarized and discussed.

Impact ionization at very low voltages in silicon

Impact ionization in germanium and silicon has been the subject of extensive theoretical and experimental work. The general agreement in the literature for the value of the threshold energy for impact ionization is 1.5 times the energy gap (EG) at room temperature which corresponds to 1.65 eV in the case of silicon. In this work, using a metal semiconductor field effect transistor (MOS device), as a sensitive tool for detecting small multiplication currents, impact ionization is investigated in a region where the total potential drop over which carriers are accelerated is less than the threshold energy for impact ionization. Impact ionization currents are detected for potential drop as low as 1.1 V. The positive temperature coefficient in this region suggests that the initial thermal distribution of the electrons dominates impact ionization for very low accelerating voltages.

Threshold energies for impact ionization by electrons and holes in InP

The threshold conditions for impact ionization in InP at 300 K have been calculated from the electronic band structure along the three major symmetry axes. These calculations show that conditions for electron-initiated impact ionization in InP are much more favorable than in GaAs.

Threshold energy for impact ionization by electrons in GaAs considering the nonparabolicity of the central valley

A theoretical calculation of the threshold energy for impact ionization by electrons in GaAs has been presented considering the nonparabolicity of the central valley. The results obtained for the process with the lowest threshold energy differ by about 10% from those obtained by assuming a parabolic central valley. In case of other processes the difference is less marked.

Threshold energy for impact ionization by holes in GaAs

Various processes have been considered for impact ionization by holes in GaAs and the corresponding threshold energies have been reported.

Impact ionization thresholds in semiconductors

A method of deriving accurate values for impact ionization threshold energies in semiconductors from realistic band structures is described. The method is applied to two different band structures for both Si and Ge. The sensitivity of the various thresholds to the precise details of the band structure is thereby investigated, and reliable information on the thresholds in these materials is obtained. In most cases it is found that impact ionization can take place when the hot electron has an excess energy not much greater than the energy gap. This is in agreement with the conclusions of Anderson and Cromwell based on less accurate values of threshold energies calculated by a different method. Threshold energies derived from approximate band models are discussed in relation to the results for the genuine bands. It is found that the lowest thresholds are not provided correctly by such models.