Ballistic electron emission microscopy studies of the temperature dependence of Schottky barrier height distribution in CoSi2/n-Si(100) diodes formedby solid phase reaction

Ballistic electron emission microscopy (BEEM) and ballistic electron emissi on spectroscopy have been performed on polycrystalline and epitaxial CoSi2/ n-Si(1 0 0)contacts at temperatures ranging from -144 degreesC to -20 degre esC. The ultra-thin CoSi2 films (similar to 10 nm) were fabricated by solid state reaction of a single layer of Co (3 nm) or a multilayer of Ti (1 nm) /Co (3 nm)/amorphous-Si(1 nm)/Ti (1 nm) with a Si substrate, respectively. The spatial distribution of barrier height over the contact area obeys a Ga ussian function at each temperature. The mean barrier height increases almo st linearly with decreasing temperature with a coefficient of -0.23 +/- 0.0 2 meV/K For polycrystalline CoSi2/Si diodes and -0.13 +/- 0.03 meV/K for ep itaxial diodes. This is approximately equal to one or one-half of the tempe rature coefficient of the indirect energy gap in Si, respectively. It sugge sts that the Fermi level is pinned to different band positions of Si. The w idth of the Gaussian distribution is about 30-40 meV, without clear depende nce on the temperature. The results obtained from conventional current-volt age and capacitance-voltage (I-V/C-V) measurements are compared to BEEM res ults. (C) 2000 Elsevier Science Ltd. All rights reserved.