Двойная лавинная инжекция в диодных лавинных обострителях

Numerical simulations of picosecond-range avalanche sharpening diodes commutating fast-rising high-voltage pulses of submicrosecond duration is performed. It is demonstrated that the maximum duration of the commutated pulse is limited by physical phenomena related to the structure transition to the double avalanche injection mode but not by the drift extraction of nonequilibrium electron-hole plasma. Double avalanche injection is in principle capable of supporting the diode structure in the conducting state after switching. However, negative differential conductivity that is attributed to the double injection mode cause transverse instability of uniform current flow and isothermal current filamentation.

Nonequilibrium electron relaxation in graphene

We apply memory function formalism to investigate nonequilibrium electron relaxation in graphene. Within the premises of two-temperature model (TTM), explicit expressions of the imaginary part of the memory function or generalized Drude scattering rate (1/[Formula: see text]) are obtained. In the DC limit and in equilibrium case where electron temperature (Te) is equal to phonon temperature (T), we reproduce the known results (i.e., 1/[Formula: see text][Formula: see text]T4 when T[Formula: see text][Formula: see text] and 1/[Formula: see text][Formula: see text]T when T[Formula: see text][Formula: see text], where [Formula: see text] is the Bloch–Grüneisen temperature). We report several new results for 1/[Formula: see text] where T[Formula: see text][Formula: see text][Formula: see text]Te relevant in pump–probe spectroscopic experiments. In the finite-frequency regime we find that 1/[Formula: see text] when [Formula: see text], and for [Formula: see text] it is [Formula: see text]-independent. These results can be verified in a typical pump–probe experimental setting for graphene.