Effect of Radiation Source on the Degradation in Irradiated Si1−xGex Epitaxial Devices

Abstract

Irradiation damage in n+-Si/p+−Si1−xGex epitaxial diodes and n+-Si/p+-Si1-xGex/n-Si epitaxial heterojunction bipolar transistors (HBTs) is studied as a function of germanium content, radiation source, and fluence. The degradation of electrical performance of the devices by irradiation increases with increasing fluence, while it decreases with increasing germanium content. The induced lattice defects in the Si1-xGex epitaxial layer and Si substrate are studied by DLTS methods. In the Si1-xGex epitaxial layer of diodes and HBTs, an electron capture level which is associated with interstitial boron is induced by irradiation, while electron capture levels corresponding to E center and divacancy are formed in the collector region for HBTs. The impact of the radiation source on the degradation of performance is correlated with simulations of the number of knock-on atoms and the nonionizing energy loss (NIEL).