On the degradation of 1-MeV electron irradiated Si1-xGe x diodes

The degradation of n⁺-Si/p⁺-Si_1-xGe_x diodes, which are fabricated on strained Si_1-xGe_x epitaxial layers grown on conventional p-type Si substrates, is investigated through the study of the annealing behaviour of forward and reverse diode current and the electrically active defects induced in the Si_1-xGe_x 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 Si_1-xGe_x 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 behaviour, 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