Threshold LET for SEU induced by low energy ions

Simulations to determine the threshold LET as a function of the length of t he ion track are consistent with there being two regions of charge collecti on. In the top layer which contains the depletion region all the charge gen erated is collected in time to upset the device. In the next layer, 10% to 20% of the charge generated is collected and contributes to upsetting the d evice. This second layer of partial charge collection may significantly imp act the accuracy of SEU predictions involving low-energy neutrons and proto ns. A simple method of including this contribution in calculations is propo sed.