Ultrahigh Si+ implant activation efficiency in GaN using a high-temperature rapid thermal process system

Si+ implant activation efficiencies above 90%, even at doses of 5 x 10(15) cm(-2), have been achieved in GaN by rapid thermal processing at 1400-1500 degrees C for 10 s. The annealing system utilizes molybdenum intermetallic heating elements capable of operation up to 1900 degrees C, producing high heating and cooling rates (up to 100 degrees C s(-1)). Unencapsulated GaN shows severe surface pitting at 1300 degrees C and complete loss of the film by evaporation at 1400 degrees C. Dissociation of nitrogen from the surface is found to occur with an approximate activation energy of 3.8 eV for GaN (compared to 4.4 eV for AlN and 3.4 eV for InN). Encapsulation with either rf magnetron reactively sputtered or metal organic molecular beam epitaxy-grown AIN thin films provides protection against GaN surface degradation up to 1400 degrees C, where peak electron concentrations of similar to 5x10(20) cm(-3) can be achieved in Si-implanted GaN. Secondary ion mass spectrometry profiling showed little measurable redistribution of Si, suggesting D(Si)less than or equal to 10(-13) cm(2) S-1 at 1400 degrees C. The implant activation efficiency decreases at higher temperatures, which may result from Si-Ga to Si-N Site switching and resultant self-compensation. (C) 1998 American Institute of Physics. [S0003-6951 (98)03828-5].