Transient current mapping obtained from silicon photodiodes using focused ion microbeams with several hundreds of MeV

Hirao, Toshio; Onoda, Shinobu; Oikawa, Masakazu*; Sato, Takahiro; Kamiya, Tomihiro; Oshima, Takeshi

Single-Event Effects (SEEs) are triggered when an energetic heavy ion traverses a sensitive area in electric devices. Since the SEEs occur due to dense charge which is created along to ion track within the order of picoseconds, the measurement of such a high speed current signals is very important. Furthermore, the size of dense charge and their concentration depend on LET as well as energy of incident ions. This means that the transient currents induced in electronic devices by incidence of ions with various energies and LETs should be investigated to clarify the mechanism of SEEs for electronic devices. Especially, the evaluations using heavy ions with high energies more than a several hundred MeVs are very important to understand the mechanism of SEEs observed in space. For this aim, we have developed an irradiation system of focused heavy ion microbeams at a several hundreds of MeVs at JAEA. In this paper, we study transient currents induced in Si photodiodes using the focused heavy ion microbeam irradiation system. The mapping of charge collected from the photodiodes irradiated with 260 MeV Ne ion microbeams, which is firstly observed in the world, will be presented. In addition, the difference in transient currents induced by ions at several hundred MeVs from ions at tens MeVs is discussed using TCAD (Technology Computer Aided Design) and GUN theorem.