Characterization of breakdown phenomena in light emitting silicon n⁺p diodes

A 10 kV, 10^-10 A focused electron beam was used to map localized charge multiplication, and localized avalanche breakdown sites in the depletion region of light emitting silicon n⁺p junctions. It was observed that the localized avalanche breakdown sites led to the formation of large densities of extremely small current filaments in the junction. The dimension of each filament was well into the submicron range (100-150 nm in diameter) and the densities of the filaments varied laterally across the junction between 4×10⁸ and 4×10¹⁰ cm^-2. Accurate and high resolution maps of the current filaments could be obtained. The formation of the individual current filaments (microavalanche sites) at a submicron level are apparently related to localized defect and materials effects. The distribution of the current filaments at the micron level relates to the strength and distribution of electric field at the junction interface. Direct evidence has been obtained that the nonuniformities in the light emission patterns on a larger scale (10-100) microns are controlled by dopant striations on the lower doped p-side of the diode junction.