Impact ionization by electrons and holes in InP

• Published in: Solid-state electronics 1980-01, Vol.23 (8), p.881-891
• Main Authors: Chung-Whei Kao, Crowell, C.R.
• Format: Article
• Language: English
• ISSN: 0038-1101; 1879-2405
• DOI: 10.1016/0038-1101(80)90106-9

Ionization coefficients of holes in InP exceed those of electrons by a factor of approximately four over the electric field range from 2.5 to 4.5 × 10 5 V/cm and have been measured in Pt on p-type 〈100〉 orientation InP Schottky diodes. The shape of the baseline for the hole induced multiplication has been fitted by using one adjustable parameter, namely: the mean free path for optical phonon scattering. The model includes effects of quantum mechanical transmission, barrier height lowering and phonon scattering before the barrier maximum. The shape of the baseline for electron multiplication was likewise fitted by one adjustable parameter: the minority carrier diffusion length. Both models produce an excellent fit to low field characteristics that have appreciable curvature. The average phonon scattering mean free path for holes is ∼ 35 A ̊ roughly consistent with that required to characterize the hole ionization coefficient. The electron diffusion length in p-type InP was found to be ∼ 18 μ for all diodes. Ionization coefficients were obtained for diodes in the doping range from 5.0 × 10 15 to 7.8 × 10 15 cm −3. The impact ionization curves were fitted by Baraff-Chwang curves with slightly field dependent average energies for pair production. The threshold energies have been calculated from a consideration of energy and momentum conservation in a theoretical band structure. The deduced mean free paths for phonon scattering and breakdown voltages calculated from the ionization coefficient measurements are in excellent agreement with other independent experiments.