Hydrogen contamination and defect generation in P-type silicon and silicon-germanium Schottky barrier test structures

The introduction of hydrogen into silicon during normal cleaning procedures together with defect generation during the deposition of Schottky barriers can result in very serious misinterpretations of C-V and DLTS data. We first show that the passivation of dopants by hydrogen (introduced by wet cleaning) may induce an apparent non-uniform carrier distribution even though the actual dopant distribution is uniform. We then show how the electrical activity of the dopant can be recovered by a simple procedure. As an example such recovery of electrical activity is demonstrated in relation to a SiGe-based heterostructure. We also show that the fabrication procedure of test-diodes may generate electrically-active defects which are induced when sputtering is used as the metallisation technique in Schottky diode fabrication. Impurities, such as dopants and hydrogen, are also involved in the formation of these defects. The distribution of these impurities prior to the sputtering process is shown to influence greatly the final defect distribution.