High-resistivity regions in n -type InGaAsP produced by ion bombardment at different temperatures

The formation of high-resistivity regions in Si-doped (n=1×1018 cm−3) lattice-matched In0.75Ga0.25As0.54P0.46 on InP by nitrogen and boron ion irradiations at 300 K, and by helium ion bombardment at 80, 300, and 523 K has been investigated as function of ion dose (1×1012–1×1016 cm−2) and subsequent anneal temperature (70–650 °C) by sheet resistance and Hall effect measurements. The dose dependence of the sheet resistance shows two regions for all cases considered: (I) for lower doses in which the sheet resistance (resistivity) increases up to a maximum of about 6×106 Ω/⧠ (180 Ω cm), and (II) for higher doses in which the sheet resistance decreases with dose. Temperature dependent Hall measurements for materials in region (I) show thermally activated carrier densities with activation energies between 0.21 and 0.29 eV. The temperature dependence of the sheet resistance in region (II), on the other hand, is consistent with the assumption of a hopping conductivity. Varying the substrate temperature during the irradiations yields no measurable effects for samples implanted in region (I). For the case of He+ bombardments at 523 K, higher sheet resistances are obtained in region (II) as compared to samples irradiated at lower temperatures. For the case of He+ at 80 K and N+ at 300 K a third region (III) is observed for doses higher than 7 and 2×1014 cm−2, respectively, in which a renewed increase in the sheet resistance with increasing dose is detected. Rutherford backscattering-channeling results suggest that this behavior is related to the creation of an amorphouslike region in the InGaAsP layer. Annealing of samples amorphized by He+ at 80 K yields higher resistivities (up to a factor of 6×105 relative to that of the unimplanted material), and improved stability of the high resistivity as compared to the other implantation schedules investigated.