Electrical properties of He+ ion-implanted GaInP

The electrical properties of high resistivity GaInP layers produced by He⁺ ion implantation have been studied. Thick high-resistivity layers (ρ > 10⁷ Ω-cm) were obtained using multi-energy implants (80 keV, 120 keV, and 150 keV). Current-voltage (I-V) measurements of mesa diodes with two ohmic contacts indicate that in the temperature range from 200 to 300K, the dominant current flow mechanism in both n-type and p-type implanted materials is Poole-Frenkel emission, especially in the range of high electric field (>10⁵ V/cm). The thermal activation energy E_a and the potential barrier height Φ_o of the generated deep levels are 0.16±0.005 eV and 0.33±0.005 eV, respectively. At low temperature, the hopping current dominates at low and moderate applied electric fields, and the I-V curves show an ohmic characteristic. The high-temperature annealing behavior of the implanted GaInP indicates that the compensation of free carriers in the material is dominated by damage-related levels, which are annealed out at high temperatures. In regard to typical alloying cycles of metal contacts in device fabrication, it is worth noting that the resistivity is still as high as 2 × 10⁸ Ω-cm for n-type samples (5 × 10⁷ Ω-cm for p-type) after 350°C annealing, which suggests that multi-energy He⁺ implantation is suitable for implant isolation in the GaInP device technology.