Proton irradiation effects on the performance of Si1-xGex devices

Irradiation damage in n + -Si/p + -Si 1-x Ge x /n-Si epitaxial diodes and heterojunction bipolar transistors (HBTs) by protons is studied as a function of germanium content, proton fluence and energy for the first time. The degradation of the electrical performance of devices increases with increasing fluence, while it decreases with increasing germanium content and energy. The induced lattice defects in the Si 1-x Ge x epitaxial layers and the Si substrate are studied by DLTS methods. In the Si 1-x Ge x epitaxial layers for diodes, electron capture levels associated with interstitial-substitutional boron complex are induced by irradiation, while two electron capture levels corresponding to the E center and the divacancy are observed in the collector region of the HBTs. The influence of the radiation source on device degradation is then discussed taking into account the number of knock-on atoms and the nonionizing energy loss (NIEL). The radiation source dependence of performance degradation is attributed to the difference of mass and the probability of nuclear collision for the formation of lattice defects.