rs that survive recombination is independent of the PKA energy, and (2) the resulting stable defects have the same device effect regardless of whether they evolved from a vacancy-interstitial pair originating in a subcascade or as a well-separated pair [Dale88]. In addition, given that various stable defects have quite IV-63 different electrical properties, the correlation also implies that the defect inventory produced is independent of PKA spectrum. Nevertheless, the degree to which the NIEL correlation holds is qualitatively consistent with the Monte Carlo calculations described earlier. These simulations show that a higher energy PKA will produce more overall damage, but that the microscopic nature of the damage is not drastically different. The branching process simply creates more and more subcascades, each separated by a string of relatively isolated defects. It is still important to keep in mind that, although defects produced from isolated vacancy-interstitial pairs (such as those produced by gamma rays and 1 MeV electrons) may have similar electrical characteristics to those produced by heavier particles such as protons and neutrons, there are important differences. These differences are not restricted to short term annealing effects, and also manifest themselves in the long term behavior of a device. For example, E-centers (vacancy-phosphorus defects) produced by 1 MeV electrons anneal at a significantly lower temperature than those produced by protons [Walk73, Kime79], a relevant (and unfortunate) fact for charge coupled device (CCD) engineers who have considered on-orbit warm-ups to mitigate charge transfer efficiency degradation in CCDs [Holl91a]. Differences in the operation of SiGe transistors [Rold98] and AlGaAs/GaAs solar cells [Barn84] have been attributed to differences in the defects produced by neutrons versus protons. Very well controlled deep level transient spectroscopy studies [Eise92, Mind76] have unequivocally demonstrated that, although 1 MeV electrons and protons produce some of the 