It was recalled that unintentional Zn diffusion during metalorganic vapor-phase epitaxy could cause serious damage in semiconductor devices. Diffusion of unintentionally diffused Zn atoms, from a p-type InP layer to the adjoining InP substrate during the growth of the p-type layer was monitored by means of secondary ion mass spectrometry. Diffusion profiles with a double diffusion front, which was composed of a shallow front with a high Zn concentration and a deep front with a low Zn concentration, were investigated. The diffusion depth of each front was proportional to the Zn dosage, which was based upon the Zn concentration; with no regard to the saturation limit. The diffusion depth for a growth time of 1h increased in proportion to the Zn dosage, at a rate of 1.6 x 10-19μcm3 for the shallow front and 3.2 x 10-19μcm3 for the deep front; at a growth temperature of 600C. The deep front extended twice as fast as the shallow front; which was normally seen as a p-n junction. The Zn concentration at which unintentional Zn diffusion occurred was deduced to be higher than 2 x 1017/cm3. Therefore, the penetration of Zn into the active region of semiconductor devices was to be expected when unintentional diffusion took place. A kick-out mechanism was suggested to explain the diffusion coefficient for unintentional diffusion; even at low Zn concentrations.

Control of Double Diffusion Front Unintentionally Penetrated from a Zn-Doped InP Layer during Metalorganic Vapor Phase Epitaxy N.Otsuka, M.Kito, M.Ishino, Y.Matsui, F.Toujou: Journal of Applied Physics, 1998, 84[8], 4239-47