DEGRADATION AND RECOVERY OF PROTON-IRRADIATED SI1-XGEX EPITAXIAL DEVICES

Irradiation damage in n(+)-Si/p(+)-Si1-xGex/n-Si epitaxial diodes and heterojunction bipolar transistors (HBTs) by protons is studied as a f unction of germanium content, proton fluence and energy for the first time. The degradation of the electrical performance of devices increas es with increasing fluence, while it decreases with increasing germani um content and energy. The induced lattice defects in the Si1-xGex epi taxial layers and the Si substrate are studied by DLTS methods. In the Si1-xGex epitaxial layers for diodes, electron capture levels associa ted with interstitial boron complex are induced by irradiation, while two electron capture levels corresponding to the E center and the diva cancy 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 degradatio n is attributed to the difference of mass and the probability of nucle ar collision for the formation of lattice defects. In order to examine the recovery behavior, isochronal thermal annealing is carried out fo r temperatures ranging from 75 to 300 degrees C. Based on the recovery of electrical performance, it is pointed out that the electron captur e levels induced in the Si1-xGex epitaxial layers are mainly responsib le for the increase of reverse diode current.