SILICON IMPLANTATION IN GAAS

The electrical properties of room-temperature Si implants in GaAs have been studied. The implantations were done at 300 keV with doses ranging from 1.7×1013 to 1.7×1015 cm-2. The implanted samples were annealed with silicon nitride encapsulants in H 2 atmosphere for 30 min at temperatures ranging from 800 to 900°C to electrically activate the implanted ions. Results show that the implanted layers are n type, which implies that the Si ions preferentially go into Ga sites substitutionally. For low-dose implants, high (∼90%) electrical activation of the implanted ions is achieved and the depth distribution of the free-electron concentration in the implanted layer roughly follows a Gaussian. However, for high-dose implants, the activation is poor (<15% for a 900°C anneal) and the electron concentration profile is flat and deeper than the expected range.