Novel ways to grow thermally stable semi-insulating InP-based layers

Abstract

Semi-insulating InP is generally grown by Fe doping. In contact with p-type layers, however, semi-insulating characteristics turn out to be difficult to reproduce because of pronounced interdiffusion of Fe and p-type dopants. Co-doping of InP:Fe with Ti is shown to be a universal process for the preparation of thermally stable high-resistivity layers. Fe + Ti co-doping can compensate both excess shallow donors and excess shallow acceptors up to concentrations of 8 × 10 16 and 2 × 10 16 cm -3, respectively. In contrast to InP:Fe, resistivities in excess of 10 7 Ω cm are obtained in contact with both symmetric n- and p-type current injecting contacts. Moreover, co-doping of semi-insulating InP:Fe with Ti is found to suppress the interdiffusion of Fe and p-type dopants. Therefore, the out-diffusion and accumulation of Fe in other regions of complex device structures can be significantly reduced. A comprehensive model accounting for these phenomena is presented. A totally different way to produce thermally more stable semi-insulating InP layers is to replace Fe by a less diffusive deep acceptor. We propose the 4d transition metal Rh as a potential alternative. The diffusion of Rh is shown to be practically nonexistent and near-midgap Rh levels are found by means of DLTS in InP at E v + 730 meV and in InGaAs at E c - 380 meV below the conduction band. We conclude these levels to be the single acceptor states of Rh substitutionally incorporated on cation sites.