Intense terahertz pulse-induced impact ionization and electron dynamics in InAs

Abstract

Electron dynamics and impact ionization are investigated by Monte Carlo method in n-type InAs exposed to intense ultrashort terahertz pulse at 300 K temperature. The sequence of hot electron transfer between the Γ and upper L and X valleys is established: hot electrons of the Γ valley transfer firstly to the L valley, and then they are scattered to the X valley. Electron population in the valleys and characteristic time of their redistribution between the Γ, L and X valleys is investigated in strong electric fields. It is found that the threshold electric field of impact ionization increases with shorter THz pulses. The process of impact ionization is shown to be the dominant energy loss mechanism of hot electrons having energy larger than the threshold energy of impact ionization. Good agreement between the results of calculation and available experimental data is demonstrated.

Competition between isotropic and strongly anisotropic terms in the impact ionization rate of narrow- and middle-gap cubic semiconductors

“…Since in practice the output characteristics arising from impact ionization depend on many details, including specific band structure of a given material and characteristics of the relaxation processes giving a particular form of the non-equilibrium distribution function, the problem of calculation, say, of the I-V characteristics, starting directly from a band structure model is in no sense easy, from both conceptual and technical points of view. Therefore, the most popular method for modelling is Monte Carlo [3][4][5][6][7][8][9][10][11][12][13] , but it is obviously dependent on a particular relation between the impact ionization rate and the a) Electronic mail: afanasiev.an@mail.ru energy of a hot electron initiating the process, W(E). Phenomenologically, the rate must grow like a power of the excess energy above a threshold,…”