Secondary ion mass spectroscopy study of Al diffusion in sandwich-ZnSTe structures grown by molecular beam epitaxy

Sandwiched structures that consist of ZnSTe/ZnSTe:Al/ZnSTe were fabricated by the molecular beam epitaxy technique on three GaAs substrates oriented along (100), (511), and (711), respectively, to study the thermal diffusion of Al dopant in ZnS0.986Te0.014 matrix by secondary ion mass spectroscopy depth profiling. The relative sensitivity factor of Al respect to Zn was determined to be 4.5 +/- 0.5x10(19) cm(-3). The Al diffusion coefficients at annealing temperature of 450 and 550 degrees C were found to be dependent on Al concentration. The upper and lower limits of the diffusion coefficients were obtained through a data fitting program based on Fick's second law, the results suggest that the diffusion is anisotropic possibly due to channeling effect. The results also reveal that Al in the matrix is thermally stable at temperature as high as 300 degrees C and thus prove that Al is a good candidate for the n-type doping of ZnSTe alloy system in terms of thermal stability. (C) 1999 American Institute of Physics. [S0021-8979(99)01917-9].