On the degradation of 1-MeV electron irradiated Si(1-x)Gex diodes

The degradation of N+-Si/p+-Si1-xGex diodes, which are fabricated on strained Si1-xGex epitaxial layers grown on conventional p-type Si substrates, is investigated through the study of the annealing behavior of forward and reverse diode current and the electrically active defects induced in the Si1-xGex epitaxial layers. The diodes are irradiated at room temperature with 1-MeV electrons with fluences ranging from 1014 to 1015 e/cm2 in a high voltage transmission electron microscope. The germanium fraction of the Si1-xGex epitaxial layer used for the diodes in this study is x = 0.12 and 0.16. The degradation of the diode performance and the presence of deep levels are investigated as a function of electron fluence and germanium content. The degradation of the x = 0.12 diodes is more remarkable than that of the x = 0.16 diodes. In order to examine the recovery process, isochronal thermal anneals are performed in the temperature range between 100 and 350 C. From the annealing behavior, it is pointed out that the electron capture levels, which are related with interstitial boron, are mainly responsible for the increase of reverse and forward current