10.3 Exciton Recombination
317
(a)
(b)
Fig. 10.16 a Photoluminescence spectra (T = 80 K, scaled) of three Mg x Zn 1−x O alloy layers on sapphire with three
different Mg-contents, x = 0.005, x = 0.03, and x = 0.06 as labeled. The energy positions of (D 0 ,X) and X A peaks
are marked. Adapted from [977]. b Peak energy of the photoluminescence spectrum (T = 2 K) of ZnO (I 6 -line, star)
and various Mg x Zn 1−x O alloys (circles). For x ≤ 0.03 (filled circles) the (D 0 ,X) recombination peak (Al donor) can be
spectrally separated from the free exciton (X A ) recombination. For the samples with higher Mg content (empty circles)
a single recombination peak is present at all temperatures. The dashed line is a linear least square fit for the alloys with
0 ≤ x ≤ 0.03, showing that also for x > 0.03 the low temperature recombination peak is due to donor-bound excitons.
Adapted from [988]
Fig. 10.17 Temperature dependence of the shift of energy position of (D 0 ,X) and X A photoluminescence peak in
Mg x Zn 1−x O alloys with three different Mg-contents, (a) x = 0.005, (b) x = 0.03, (c) x = 0.06. The energy positions
are given relative to the low temperature position of the respective (D 0 ,X) peaks. Adapted from [977]
the inhomogeneous broadening of σ = 2.6 meV. At low temperature the luminescence intensity is
dominated by (D
0 ,X) recombination, at room temperature by free exciton (X A ) recombination. Both
peaks are present at low temperatures and exhibit a red-shift with increasing temperatures due to the
shrinking of the band gap (Fig. 10.17a). The (D
0 ,X) peak vanishes at about 180 K due to ionization of
the excitons from the donors (Q ≈ 15 meV, similar as in pure ZnO).
For larger Mg-content of x = 0.03 the two peaks can still mostly be separated (σ = 6.0 meV).
The (D
0 ,X) energy position shows a small dip (about 2 meV) due to exciton localization in the alloy
317
(a)
(b)
Fig. 10.16 a Photoluminescence spectra (T = 80 K, scaled) of three Mg x Zn 1−x O alloy layers on sapphire with three
different Mg-contents, x = 0.005, x = 0.03, and x = 0.06 as labeled. The energy positions of (D 0 ,X) and X A peaks
are marked. Adapted from [977]. b Peak energy of the photoluminescence spectrum (T = 2 K) of ZnO (I 6 -line, star)
and various Mg x Zn 1−x O alloys (circles). For x ≤ 0.03 (filled circles) the (D 0 ,X) recombination peak (Al donor) can be
spectrally separated from the free exciton (X A ) recombination. For the samples with higher Mg content (empty circles)
a single recombination peak is present at all temperatures. The dashed line is a linear least square fit for the alloys with
0 ≤ x ≤ 0.03, showing that also for x > 0.03 the low temperature recombination peak is due to donor-bound excitons.
Adapted from [988]
Fig. 10.17 Temperature dependence of the shift of energy position of (D 0 ,X) and X A photoluminescence peak in
Mg x Zn 1−x O alloys with three different Mg-contents, (a) x = 0.005, (b) x = 0.03, (c) x = 0.06. The energy positions
are given relative to the low temperature position of the respective (D 0 ,X) peaks. Adapted from [977]
the inhomogeneous broadening of σ = 2.6 meV. At low temperature the luminescence intensity is
dominated by (D
0 ,X) recombination, at room temperature by free exciton (X A ) recombination. Both
peaks are present at low temperatures and exhibit a red-shift with increasing temperatures due to the
shrinking of the band gap (Fig. 10.17a). The (D
0 ,X) peak vanishes at about 180 K due to ionization of
the excitons from the donors (Q ≈ 15 meV, similar as in pure ZnO).
For larger Mg-content of x = 0.03 the two peaks can still mostly be separated (σ = 6.0 meV).
The (D
0 ,X) energy position shows a small dip (about 2 meV) due to exciton localization in the alloy