Abstract:
We provide evidence that the Tm3+ -induced defects in Tm-doped AlxGa1-xN hosts play a major role in the nonradiative transfer of the excitation energy from the I16 state to the D12 state of Tm3+ ions from which the most efficient photoluminescence (PL) transition (465 nm) occurs. Once the concentration of the Tm3+ -induced defects decreases with increasing x , the PL transitions starting from the I16 state (298, 357, 395, 530, and 785 nm) may be significantly enhanced. It is shown that the indirect excitation of the I16 state results from the Auger-type energy transfer due to the nonradiative band-to-band recombinations in the AlxGa1-xN host of a given x . In contrast, the PL transitions starting from the G14 level (479 and 807 nm) can be excited through either an indirect or a direct regime. In both cases the G14 level is populated by the radiative relaxation of the higher energy excited states I16 , P30 , P31 , and P32 of Tm3+ ions.
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