Ultra-Shallow Doping of GaAs with Mg, Cr, Mn and B Using Plasma Stimulated Room-Temperature Diffusion

It is demonstrated that Mg, Cr, Mn and B can be doped close to GaAs surface by plasma doping without external bias at room temperature (RT). The process only takes a few minutes, and impurity densities in the range of 10₁₈-10₂₁/cm₃ can be achieved with doping depths about twenty nanometers. The experiment results are analyzed and the physical mechanism is tentatively explained as follows: during the doping process, impurity ion implantation under plasma sheath voltage takes place, simultaneously, plasma stimulates RT diffusion of impurity atom, which plays the main role in the doping process. The enhanced RT diffusion coefficients of Mg, Cr, Mn and B in GaAs are all in the order of magnitude of 10_-15 cm₂sec_-1. This is reported for the first time among all kinds of plasma assisted doping methods.