Photoluminescence and Raman studies of silicon ion implantation annealing in GaAs

Double implantation of Si-29 has been employed for n(+) source - drain and channel formation in SI - GaAs on the basis of TRIM calculations. Rapid thermal annealing (RTA) has been carried out thereafter on samples at three temperatures : 900(0) C for 25 s, 925(0) C for 10s and 950(0) C for 6s to examine conditions for obtaining lowest sheet resistivity and highest activation efficiency. Four - point probe resistivity mapping, C - V profiling and Hall studies showed that the lowest sheet resistivity of 164.2 ohms / square with Hall mobility of 2800 cm(2) / V.s and highest activation efficiency of 50 % was obtained for RTA at 925(0) C for 10s. Photoluminescence (PL) was carried out to determine the location of implanted Si atoms. The intensity of the PL line at 12 K due to band - acceptor (Si) transition at 1.476 eV was compared with that due to band - acceptor (C) transition at 1.497 eV, Carbon (C) being a constant background impurity in all the samples. This ratio, and hence the compensation, was found to go through a minimum far RTA at 925(0) C, in agreement with the results of electrical studies for optimum implant activation. Raman studies showed the presence of the LO mode and the L+ and L. plasmon modes. From their frequencies the electron concentrations in the samples after annealing at 900(0) C, 925(0) C and 950(0) C were determined to be 4.47 x 10(17) / cm(3), 6.3 x 10(17)/ cm(3) and 5.05 x 10(17) / cm(3) respectively, in good agreement with resistivity measurements.