Single-carrier impact ionization favored by a limited band dispersion

Abstract

A critical requirement for high gain and low noise avalanche photodiodes is the single-carrier avalanche multiplication. We propose that the single-carrier avalanche multiplication can be achieved in materials with a limited width of the conduction or valence band resulting in a restriction of kinetic energy for one of the charge carriers. This feature is not common to the majority of technologically relevant semiconductors, but it is observed in chalcogenides, such as Selenium and compound I 2 -II-IV-VI 4 alloys.

Modeling the radiation ionization energy and energy resolution of trigonal and amorphous selenium from first principles

“…The Brillouin zone was sampled using a Monkhorst-Pack [19] 20 × 20 × 18 k-point mesh. Further details regarding the geometry of the model structure and convergence criteria have been reported elsewhere [12,20].…”

“…The threshold energies for electrons and holes are derived from analysis of the t-Se band structure taking into account energy and momentum conservation requirements [12]. The results of the calculation suggest that the ionization threshold in t-Se is approximately equal to the energy gap (E th,e = E g and E th,h = 1.05E g [12]).…”

“…The threshold energies for electrons and holes are derived from analysis of the t-Se band structure taking into account energy and momentum conservation requirements [12]. The results of the calculation suggest that the ionization threshold in t-Se is approximately equal to the energy gap (E th,e = E g and E th,h = 1.05E g [12]). This result differs significantly from that predicted by the parabolic band approximation (E th = 1.5E g ) and can be attributed to the indirect band structure of t-Se.…”

“…Recent analysis of the electronic structure of trigonal selenium (t-Se) indicates that E th ≈ E g for both types of charge carriers as a result of the indirect band structure [12]. Therefore, the assumption regarding violation of momentum conservation is not necessarily required for interpretation of the low W 0 ± in a-Se.…”