On the origin of slow domains in GaAs:O

Measurements between 90K and 200K of the field outside the domain, the domain velocity, and other entities associated with slow domains in n-type GaAs:O (2 Omega cm at 300K) are shown to point unambiguously to the origin of the associated negative differential resistance. This origin is an impurity-barrier mechanism connected with trapping at Gaussian-broadened complex of levels peaking near 0.05 eV below the conduction band. The natures of the barrier and centre are unknown. It is shown that if the barrier is taken to be unscreened Coulombic originating in a negative charge of magnitude Ze then the measured activation energy (0.077 eV) entails Z=10, which appears unacceptably high.