Implant-induced high-resistivity regions in InP and InGaAs

Abstract

We have investigated the effects of ion bombardment on the electrical properties of intentionally doped InP and InGaAs grown by metalorganic molecular-beam epitaxy. The sheet resistivity and mobility of n+InP (Sn) and n+InGaAs (Sn) or p+InGaAs (Be) epilayers grown on semi-insulating InP substrates were measured as a function of ion species (O, B, H, or Fe), ion dose (1012–1015 cm−2), and post-implant annealing temperature (100–600 °C). In n+InP, the resistivity after bombardment goes through a maximum with annealing temperature, reaching a value of ∼106 Ω/⧠ for 0.5-μm-thick films after implantation with H or O and annealing at 200–300 °C. The as-grown resistivity is restored by annealing above 500 °C. Ion doses below 1012 cm−2 actually lead to a decrease in resistivity through the creation of shallow donor levels. By contrast, the implantation of Fe above a critical dose where the Fe density exceeds the dopant concentration leads to the formation of thermally stable, high-resistivity (>106 Ω/⧠) material. The temperature dependence of the resistivity shows an activation energy of 0.67 eV, which corresponds to the acceptor level of substitutional Fe in InP. Both n+InGaAs and p+InGaAs show somewhat similar behavior after implantation with maximum resistivities of ∼105 Ω/⧠ regardless of implant species. Once again for relatively low doses of O or H (below ∼1013 cm−2 in this case) there is creation of shallow defect levels that lower the resistivity of the material. The formation of these levels in InP has been investigated in more detail by measuring the depth-dependent carrier profile in implanted high-resistivity InP. The profile of the damage-induced centers is in close correlation with the nuclear energy deposition profile of the implanted ion in some cases, and with the profiles of stoichiometric excess due to unequal recoil of the lattice constituents in other cases.