Influence of germanium content on the degradation of strained Si1−xGex epitaxial diodes by electron irradiation

The degradation of strained n+-Si/p+-Si1−xGex epitaxial diodes, which are irradiated at room temperature with 1 MeV electrons in a high-voltage transmission electron microscope, is investigated. Special attention is given to the influence of the germanium content on the degradation of electrical characteristics and on the introduction of lattice defects into the epitaxial layer. The diode degradation and the deep level density for the x = 0.12 diodes are larger than for the x = 0.16 diodes. This can be explained by the fact that germanium atoms act as recombination centres for vacancies and interstitials thus decreasing the generation rate of stable radiation defects and by the fact that the energy absorbed in the epitaxial layer during irradiation decreases with increasing germanium content due to the smaller stopping power of germanium atoms.