Abstract
Tantalum silicide films on GaAs exhibit high7 temperature stability. Itcan be used in the SAG technique to fabricate high speed MESFET. Thetantalum silicide films were investigated by XRD, AES, RBS, and van derPauw methods under various conditions of annealing process. The XRDpattern gives the mixture phases of TaSi2and Ta5Si3 for Si7 rich samplesat annealing temperature above 700℃, and a singlc phase of Ta5Si3 forTa7 rich samples. These results consist with the resistivity changeabruptly for annealing temperature at 700℃ and has a significant dropbetween 700 and 900℃. Using Rutherford backscattering spectrum, we haveobserved Ga diffusion into the TaSix layer for furnace annealing above900℃. But this outdiffusion disappears for rapid thermal annealing at900℃for 10 seconds. The I- V barrier height of TaSix/GaAs was found toremain stable at 0.7 eV, but the C- V barrier height shows a differentvalue. It can be explained by Card and rhoderick's (MIS) model. Thecarrier profile can be determined from C- V measurement. It also tells theSi diffuses from TaSi2 into GaAs for furnace annealing sample. Meanwhile,the Ga outdiffusion gives the Ga vacancies in GaAs and offset the carrierconcentration in Rapid thermal annealing sample. The interface state bothof TaSi2/GaAsand of Ta5Si3/GaAs under various annealing conditions werestudied by Deep- level transient spectroscopy, multifrequency capacitanceanalysis, C- V, and G- V techniques. The frequency dispersion of thecapacitance and conductance were observed. The G7 V measurements showseveral humps which relates to the interface state. The MIS model and thetunneling mechanism were adopted to successfully explain the aboveelectrical measurements.