Band-gap engineering for removing shallow traps in rare-earth Lu3Al5O12garnet scintillators using Ga

Structure–Property Correlations in a Ce-Doped (Lu,Gd)2SiO5:Ce Scintillator

“…For example, in accordance with [1,2], light yield in Ce-doped mixed lutetium-yttrium perovskite increases by around twice in comparison with YAlO 3 :Ce (YAP) and LuAlO 3 :Ce (LuAP). Similar phenomena were recently reported for (LuGd) 3 (Al x Ga 1-x ) 5 O 12 :Ce (LuGAGG) [3] and BaBrI:Eu [4]. A successful example of engineering of mixed rare earth orthosilicate crystals is lutetium yttrium silicate Lu 2x Y 2-2x SiO 5 :Ce (LYSO) demonstrating improvement of energy resolution and some increase in light yield in comparison with Lu 2 SiO 5 :Ce (LSO) [5,6].…”

“…In LuGAGG, the observed light yield increase can be attributed to the significant (1.6 eV) bandgap change at cation substitution in solid solution [3]. In accordance 5 with [4], adjusting the Ga content enables one to suppress the effect of shallow electron traps which become buried in the conduction band edge [4]. Increase of the scintillation efficiency can be also enabled by the decrease of the host band gap value, i.e., the decrease of energy for creation of one electron-hole pair.…”

Band-Gap and Band-Edge Engineering of Multicomponent Garnet Scintillators from First Principles

“…Figure 2 shows the relative position of the conduction band minimum (CBM) and valence band maximum (VBM), along with the lattice parameters, for each of the compounds considered. Figure 2 respect to LuAG, while the VBM is only slightly shifted and this shift in the CBM of LGG is related to the CBM shift observed in Ga-doped LuAG, which leads to the overlap of the cation antisite trap state [29]. A similar, but more pronounced, effect is observed for Lu 3 In 5 O 12 , where the CBM is further shifted with respect to LuAG and LGG, but the VBM remains near to that of LuAG and LGG.…”

“…However, Ga is closer in size to the RE cation than it is to Al [26], which suggests that a higher concentration of antisites should exist in Ga-doped garnets than in pure aluminate garnets -a hypothesis validated by a joint experimental-atomistic simulation study [27,28]. Rather, instead of reducing the concentration of deleterious antisite defects, the benefit of Ga-admixing arises arXiv:1505.01218v1 [cond-mat.mtrl-sci] 5 May 2015 from shifts in the conduction band such that it envelops the trap state in the forbidden gap associated with the antisite defect [17,29]. This is a primary example of the "band-gap engineering" approach to defect management.…”

Origin of improved scintillation efficiency in (Lu,Gd)3(Ga,Al)5O12:Ce multicomponent garnets: An X-ray absorption near edge spectroscopy study

“…13,14 The attempts to diminish the negative influence of such defects by partial substitution of Al 3+ with Ga 3+ in the LuAG:Pr have been reported. 15 Upon partial Ga 3+ substitution, the antisite-related traps were buried in the downward moving conduction band, 16 scintillation response was noticeably accelerated and somewhat enhanced light yield in the case of Ce-doped host was found. 17 Unfortunately, with increasing Ga 3+ content, thermally induced ionization of an electron from 5d 1 state to the conduction band becomes feasible around room temperature due to the reduction of ionization energy barrier, 18 which deteriorates the scintillation efficiency.…”