Disorder into Correlation: A Microscopic Mechanism for Sub-McIntyre Avalanche Noise

Avalanche multiplication is intrinsically stochastic, yet experiments reveal excess noise below the minimum predicted by McIntyre’s local-field theory. The microscopic origin of this noise suppression remains incompletely understood. We show that polar-optical-phonon emission, confined to a narrow forward cone, competes with elastic alloy scattering that diffuses field-collimated hot carriers out of the cone. Suppressed phonon cooling narrows the ionization path beyond the dead space and synchronizes successive ionizations into a dynamic staircase. This explains the low noise of Sb-based alloys and HgCdTe and makes alloy disorder a design parameter.