
528 Microwave Engineering
This mechanism discovered by Riddley, Watking and Hilsum is named after
them. This effect called negative differential conductivity effect depends on bulk
properties of SC and not on the junction.
13.5.1.2 Ridley–Watkins–Helsum Theory
It revolves around the concept of differential negative resistance (NR)
developed in bulk solid state, in III–V group compound, when a voltage
(or current) is applied to the terminals of a sample. The negative resistance
has two modes called as (i) voltage-controlled negative resistance (VCNR)
mode in which the current density can be multi-valued and (ii) current-
controlled negative ...