Control of low fe content in the preparation of semi-insulating InP by wafer annealing

A reproducible technique for preparing semi-insulating (SI) InP by high temperature annealing can only be achieved by controlled doping with Fe in a sufficient concentration for compensation. However, a successful and reproducible method to adjust the low Fe content has not been developed up to now. In this paper, we report two different experimental approaches to control the Fe content by using either precompensated starting material or an Fe source for doping via the vapor phase. InP wafers (2′ diam) which were lightly predoped with Fe ([Fe] < 5 × 10¹⁵ cm⁻³) during liquid encapsulated Czochralski (LEC) growth were converted from the semiconducting to the SI state and were subsequently analyzed by laterally resolved resistivity measurements. These wafers show high resistivity uniformity (p ≈1 × 10⁸ Ω-cm) which has never previously been achieved with LEC material at such a low Fe concentration. Furthermore, we present the first results of annealing nominally undoped InP with a defined Fe source.