Clarification of difference for transition between photoluminescence and cathode-luminescence based on GaMnN

GaN:Mn epilayers were grown on Al₂O₃ substrate uisng molecular beam epitaxy (MBE) and were subsequently implanted with Mn⁺ ions (1% and 10%). Photoluminescence (PL) with 1% of Mn showed that optical transitions related to Mn revealed the donor-Mn pair (D, Mn) at 2.5 eV and the electron-Mn pair (e, Mn) around 3.1 eV, and yellow luminescence (YL) around 2.20-2.25 eV. Photoluminescence (PL) with 10% of Mn showed the same but enhanced optical transitions as above. However, the new transitions around 1.65 eV for the sample with 10% which did not appeared with Mn of 1% were very weakly produced. The results of cathode-luminescence (CL) with 10% of Mn showed transitions related to Mn in PL together with new transitions around 1.72 eV. However, the new transitions around 1.72 eV for the sample with 10% according to high accelerating voltage were very remarkably activated in contrast with PL transitions which appeared were very weakly produced in samples with Mn of 10%. Transitions around 1.72 eV in CL correspond to though around 1.65 eV in PL. This result means that deep donor (probably, V_N) is detected with increasing accelerating voltage and Mn-V_N complex is formed. This is supported by strong electron beam sensitivity of the IR emission bands. It is well known that heavy Mn doping (>∼10¹⁹ C m^-3) leads to a downshift of the Fermi level and promotes the formation of defect complexes of Mn-V_N. In our case, Mn doping concentration is >∼10²¹ C m^-3. Therefore, it is conjectured that the CL transition around 1.72 eV corresponds to Mn-V_N complex.