Planar channeling in superlattices. III. Potential and parameter dependence of catastrophic dechanneling

Catastrophic planar dechanneling in strained-layer superlattices provides for a critical evaluation of fundamental-particle channeling phenomena, as well as a method of strain assessment. Using continuum-model theory, the equation of projectile motion is solved numerically. The depth and angular dependences of catastrophic dechanneling are examined as a function of the parameters: incident energy and angle, superlattice strain, crystal potential, and the minimum impact parameter for channeling. The catastrophic dechanneling increases with the strain-induced tilt angle {Δ}{ψ} and contains well-defined structures in the angular and depth dependences. These features are particularly sensitive to strain for the region {Δ}{ψ}{~}0.1 to 1.0 times the critical angle for channeling. Also, there is a range of energies ({~}±{}10%) about the resonant value for which good catastrophic dechanneling behavior is retained. Using the thermally averaged Doyle-Turner potential and data from a GaAsₓ{P}_{1{{-}}x}$/GaP superlattice, we obtain a minimum impact parameter for planar channeling of 1.3 times the Thomas-Fermi screening length. When scaled by thermal vibrational amplitude, this value (2.3${u}₁$, where ${u}₁$ is the one-dimensional amplitude) is consistent with recent computer-simulation results for the steering of particles by single-crystal planes.