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(a) CL spectra taken at of Mg-doped GaN films with different Mg concentrations. (b) Closeup of the near-band-edge region. Several transitions are observed: , , , and . The first three transitions are common in undoped GaN. There is a significant increase of the peak intensity due to an increase in Mg concentration.
CL spectrum of GaN doped with . Four Gaussian peaks were fitted to obtain the positions of the peaks. Three peaks are resolved at 3.286, 3.204, and and assigned to the main DAP peak and its two first LO phonon replica, respectively (dotted lines A, B, and C). The fourth Gaussian fit (dashed line D) is centered at and has a FWHM of .
Normalized CL transients taken at of line 1 and line 2, their positions indicated in Fig. 2, for the two Mg concentrations: (a) and (b) . In (a), the transients of lines 1 and 2 are similar. In contrast with (b), line 2 shows a slower decay as compared to line 1.
Normalized time-delayed CL spectra of Mg-doped GaN sample with Mg concentration of at various times during the luminescence decay. Two effects are observed: the redshift of line 2 (solid line) does not follow the same redshift of line 1 (dashed line) and the relative intensity of lines 1 and 2 varies during luminescence decay suggesting a second recombination process in addition to the normal DAP.
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