AIP Digital Archive
The optimum conditions for the fabrication of semi-insulating InP epitaxial layers grown by metalorganic chemical-vapor deposition are investigated in a comparative study of the structural, electrical, and diffusive properties of Fe- and Ti-doped material. Thermally stable InP:Fe layers with resistivities approaching the intrinsic limit can be prepared in an environment of n-type material if the Fe concentration does not exceed but is close to its solubility limit of 8×1016 cm−3 at 640 °C. In contact with p-type layers, however, semi-insulating characteristics of InP:Fe turn out to be difficult to reproduce because of a pronounced interdiffusion of Fe and p-type dopants. Here, Ti doping of InP is shown to be a useful scheme for the fabrication of high-resistivity layers. New processes for the deposition of InP:Ti using (C5H5)2Ti(CO)2 and Ti[N(CH3)2]4 as metalorganic precursors are described in detail. Ti is found to compensate up to 2×1016 cm−3 of shallow acceptors in metalorganic chemical-vapor-phase-deposition-grown InP. Ti-doped InP layers containing more electrically active deep Ti donors than net shallow acceptors exhibit semi-insulating characteristics with a resistivity of 5×106 Ω cm. Codoping of InP:Fe with Ti turns out to be a universal process for the preparation of thermally stable high-resistivity layers. If the material is appropriately grown, Fe+Ti doping compensates both excess shallow donors and excess shallow acceptors up to concentrations of 8×1016 and 2×1016 cm−3, respectively. In contrast to InP:Fe, resistivities in excess of 107 Ω cm are obtained in contact with both symmetric n- and p-type current injecting contacts. Moreover, codoping of semi-insulating InP:Fe with Ti is found to suppress the interdiffusion of Fe and p-type dopants. Therefore, the outdiffusion and accumulation of Fe in other regions of complex device structures can be significantly reduced. The interdiffusion of Fe and p-type dopants as well as its suppression by additional doping with Ti, finally, is studied in detail, which enables a comprehensive model accounting for this phenomenon to be developed.
Type of Medium: