On the “tunnel” diffusion of iron dopant in InP

Abstract The diffusion of iron and zinc in InP and InGaAsP during crystal growth by MOVPE is investigated. SIMS depth profiling is applied to measure the depth distribution of the dopants. Special emphasis was given to the influence of barrier layers of InP and InGaAsP between iron-doped and zinc-doped epi-layers on the diffusion of iron and zinc, respectively. Surprisingly, these barrier layers do not inhibit the diffusion and outdiffusion of iron into the zinc-doped epi-layer. However, the barrier layers remain free of dopant themselves. The dopants so to speak “tunnel” through the barriers. Furthermore, the applicability of iron-doped semi-insulating substrates is investigated. Dramatic diffusion of iron and zinc is observed with zinc-doped InP epi-layers grown on semi-insulating substrates. Epi-layers of undoped InP remain free of iron from the underlaying substrate.