Effect of Phosphine on Plasma-Induced Traps in n-InP

Electron traps in n-InP generated by exposure to Ar or phosphine (PH3) plasma have been investigated using isothermal capacitance transient spectroscopy (ICTS). One electron trap (E c-0.54 eV) is generated by Ar-plasma treatment at 250°C for 60 min. Annealing at 350°C for 3 min after Ar-plasma treatment induces another electron trap (E c-0.32 eV) together with an increase of the (E c-0.54 eV) trap density. In contrast to the case of Ar plasma, no traps are detected in InP treated with PH3 plasma consisting of Ar(90%) and PH3(10%) at 250°C for 60 min. Moreover, addition of PH3 to hydrogen (H2) plasma is shown to be effective in suppressing generation of the traps. Generation of these traps does not occur due to annealing after PH3-plasma treatment, while simple annealing of as-etched InP introduces these traps. It is demonstrated that PH3-plasma treatment leads to diffusion of phosphorus atoms during the process and deposition of a thin phosphorus layer at the surface of InP.