IRRADIATION-INDUCED LATTICE-DEFECTS IN SI1-XGEX DEVICES AND THEIR EFFECT ON DEVICE PERFORMANCE

A study is presented of the nature and influence on device performance of lattice defects in strained n(+)-Si/p(+)-Si1-xGex epitaxial diodes and n(+)-Si/p(+)-Si1-xGex/n-Si epitaxial heterojunction bipolar trans istors introduced by fast neutrons and MeV energy electrons. The gener ation of deep levels in the strained Si1-xGex epitaxial layers and the degradation of device characteristics are also reported as a function of fluence and germanium content. The degradation of device performan ce of both diodes and heterojunction bipolar transistors by irradiatio n increases with increasing fluence, whereas it decreases with increas ing germanium content. For x = 0.12 diodes irradiated by 1 MeV electro ns, hole and electron capture levels are induced in the Si1-xGex epita xial layers, although electron capture levels only are formed for x = 0.16 diodes. For x = 0.12 diodes irradiated by 1 MeV fast neutrons, on ly electron capture levels are induced. Based on the annealing behavio ur of the electrical characteristics and of the lattice defects, it is concluded that the electron capture levels which are related to inter stitial boron, are mainly responsible for the increase of reverse and forward current in 1 MeV electron irradiated diodes.