Dislocations and their Relation to Irregularities in Zinc-Diffused GaAsP p-n Junctions

The geometry of the p-n junctions formed from Zn diffusion into epitaxially grown n-type [100] GaAsP wafers is studied. In conjunction with this the dislocation structure has been investigated. For epitaxial crystals with a (100) growth plane it is shown that the predominant dislocation in the bulk is a grown-in dislocation whose axis lies in the [100] direction, perpendicular to the growth plane. By a special growth technique the bulk dislocation density may be markedly reduced in favor of an array of [110] dislocations lying adjacent to the epitaxial-substrate interface. The range of dislocation densities studied is about 0.5×106 cm−2 to 50×106 cm−2. The spiked irregularities in the Zn-diffused junctions are shown to be due to diffusion along the axes of the dislocations.