Effect of hot-carrier energy relaxation on main properties of collapsing field domains in avalanching GaAs

• Published in: Applied physics letters 2015-05, Vol.106 (18)
• Main Authors: Palankovski, V., Vainshtein, S., Yuferev, V., Kostamovaara, J., Egorkin, V.
• Format: Article
• Language: English
• Subjects: Applied physics; Avalanches; Emission; Ionization; Millimeter waves
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4921006

Multiple “collapsing” field domains are a physical reason for superfast switching and sub-terahertz (sub-THz) emission experimentally observed in powerfully avalanching GaAs structures. This phenomenon, however, has been studied so far without considering carrier energy relaxation and that essentially has restricted the possibility of correct interpretation of experimental results. Here, we apply a hydrodynamic approach accounting for non-local hot-carrier effects. The results confirm the collapsing domain concept, but show that the domains cannot reduce well below 100 nm in width, since a moving collapsing domain leaves behind it a tail of hot carriers, which causes broadening in the rear wall of the domain. This puts principal restrictions on the emission band achievable with our unique avalanche mm-wave source to about 1 THz. Another finding suggested here is a physical mechanism for the single collapsing domain's quasi-steady-state motion determined by powerful impact ionization. The results are of significance for physical interpretation of properties of our pulsed sub-THz source, which has recently demonstrated its application potential in mm-wave imaging in both amplitude and time-domain pulse modes with picosecond time-of-flight precision.