Implant isolation of InP and InGaAs by proton irradiation at variable doses and substrate temperatures

The evolution of the sheet resistance (R_s) of n-type InP and InGaAs layers bombarded by protons with doses in the range of 1×10¹²-4×10¹⁵ cm^-2 at substrate temperatures RT and 200°C was investigated. The n-type doped layers for both InP and InGaAs of thickness 1 μm were grown on semi-insulating (SI) InP substrate of <100> orientation using molecular beam epitaxy (MBE). A uniform damage density was formed within the conductive layer by proton implantation at 250 keV to isolate the structure. Resistivity and Hall effect measurements were performed to study the evolution of the sheet resistance as a function of dose. An optimum isolation of 1×10⁶ and 2×10⁴ ohms/square was obtained at a threshold dose of 4×10¹⁴ and 4×10¹⁵ cm^-2 for InP and InGaAs layers implanted at RT, respectively. For 200°C implants, a lower isolation value of ~5×10³ ohms/square was obtained at a threshold dose of 4×10¹³ and 4×10¹⁴ cm^-2 for both InP and InGaAs layers, respectively. This data suggests that, for the isolation scheme used most of the defects are already annealed out near 200°C, which explains the behaviour of the sheet resistance in the case of 200°C implants. The antisite defects formed by the replacement collisions are thought to be responsible for the isolation formed in InP and InGaAs by virtue of their lower sensitivity to dynamic annealing