“…However, this is also circumstantial and at odds with the general finding that transitions arising from states mixed with b-Ga 2 O 3 matrix states are broadened by the strong carrier-lattice coupling 18 . Lastly, similar red peaks are observed in thermally stimulated luminescence of UID 19 , Mg-doped 20 and Fe-doped 21 -Ga 2 O 3 crystals and electroluminescence of Si and Cr co-doped -Ga 2 O 3 crystals 22 and origins from Fe and Cr are claimed but also lacking detailed investigation.…”
Currently, Fe doping in the ~10 18 cm-3 range is the most widely-available method for producing semi-insulating single crystalline-Ga 2 O 3 substrates. Red luminescence features have been reported from multiple types of Ga 2 O 3 samples including Fe-doped-Ga 2 O 3 , and attributed to Fe or N O. Herein, however, we demonstrate that the high-intensity red luminescence from Fe-doped β-Ga 2 O 3 commercial substrates consisting of two sharp peaks at 689 nm and 697 nm superimposed on a broader peak centered at 710 nm originates from Cr impurities present at a concentration near 2 ppm. The red emission exhibits twofold symmetry, peaks in intensity for excitation near absorption edge, seems to compete with Ga 2 O 3 emission at higher excitation energy and appears to be intensified in the presence of Fe. Based on polarized absorption, luminescence observations and Tanabe-Sugano diagram analysis, we propose a resonant energy transfer of photogenerated carriers in-Ga 2 O 3 matrix to octahedrally-coordinated Cr 3+ to give red luminescence, possibly also sensitized by Fe 3+ .
“…However, this is also circumstantial and at odds with the general finding that transitions arising from states mixed with b-Ga 2 O 3 matrix states are broadened by the strong carrier-lattice coupling 18 . Lastly, similar red peaks are observed in thermally stimulated luminescence of UID 19 , Mg-doped 20 and Fe-doped 21 -Ga 2 O 3 crystals and electroluminescence of Si and Cr co-doped -Ga 2 O 3 crystals 22 and origins from Fe and Cr are claimed but also lacking detailed investigation.…”
Currently, Fe doping in the ~10 18 cm-3 range is the most widely-available method for producing semi-insulating single crystalline-Ga 2 O 3 substrates. Red luminescence features have been reported from multiple types of Ga 2 O 3 samples including Fe-doped-Ga 2 O 3 , and attributed to Fe or N O. Herein, however, we demonstrate that the high-intensity red luminescence from Fe-doped β-Ga 2 O 3 commercial substrates consisting of two sharp peaks at 689 nm and 697 nm superimposed on a broader peak centered at 710 nm originates from Cr impurities present at a concentration near 2 ppm. The red emission exhibits twofold symmetry, peaks in intensity for excitation near absorption edge, seems to compete with Ga 2 O 3 emission at higher excitation energy and appears to be intensified in the presence of Fe. Based on polarized absorption, luminescence observations and Tanabe-Sugano diagram analysis, we propose a resonant energy transfer of photogenerated carriers in-Ga 2 O 3 matrix to octahedrally-coordinated Cr 3+ to give red luminescence, possibly also sensitized by Fe 3+ .
“…Polarization dependence of emission is seen below the bandgap for all three samples. The observed red emission starting around 700 nm (1.77 eV) is due to the Fe-doped β-Ga 2 O 3 substrate on which the Si-doped β-Ga 2 O 3 films were grown 27 , 28 . Figure 1 Polarized photoluminescence of β-Ga 2 O 3 grown on (010) Fe-doped β-Ga 2 O 3 excited at 267 nm (4.64 eV).…”
In this work, a systematic photoluminescence (PL) study on three series of gallium oxide/aluminum gallium oxide films and bulk single crystals is performed including comparing doping, epitaxial substrates, and aluminum concentration. It is observed that blue/green emission intensity strongly correlates with extended structural defects rather than the point defects frequently assumed. Bulk crystals or Si-doped films homoepitaxially grown on (010) β-Ga2O3 yield an intense dominant UV emission, while samples with extended structural defects, such as gallium oxide films grown on either (-201) β-Ga2O3 or sapphire, as well as thick aluminum gallium oxide films grown on either (010) β-Ga2O3 or sapphire, all show a very broad PL spectrum with intense dominant blue/green emission. PL differences between samples and the possible causes of these differences are analyzed. This work expands previous reports that have so far attributed blue and green emissions to point defects and shows that in the case of thin films, extended defects might have a prominent role in emission properties.
“…В літературі опубліковано чимало робіт присвячених дослідженню енергетичних рівнів, які створені домішками і власними дефектами в забороненій зоні β-Ga2O3 поблизу краю однієї із зон [10][11][12][13][14][15]. Такі дефекти можуть захоплювати носії заряду і їх називають центрами захоплення (прилипання) або пастками [16].…”
Section: вступunclassified
“…Такі дефекти можуть захоплювати носії заряду і їх називають центрами захоплення (прилипання) або пастками [16]. Для дослідження пасток для електронів в β-Ga2O3, використовують різні методи, зокрема перехідну спектроскопію глибоких рівнів (DLTS) [10], оптичну спектроскопію глибоких рівнів [12] та термостимульовану люмінесценцію (ТСЛ) і термостимульовану провідність (ТСП) [13][14][15].…”
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