Effect of extended defects on photoluminescence of gallium oxide and aluminum gallium oxide epitaxial films

Abstract

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.

Ultraviolet Nanophotonics Enables Autofluorescence Correlation Spectroscopy on Label-Free Proteins with a Single Tryptophan

“…S3). Moreover, the gallium oxide luminescence spectrum is shifted toward 400 nm 50,51 and can be partially separated from the protein autofluorescence spectra with the 310-360 nm bandpass filter (Fig. 1g).…”

“…Gallium oxide is luminescent when excited in the UV. , This background contribution can be controlled by FIB while selecting the proper milling depth (Figure S3). Moreover, the gallium oxide luminescence spectrum is shifted toward 400 nm , and can be partially separated from the protein autofluorescence spectra with the 310–360 nm bandpass filter (Figure g). The gallium oxide photoluminescence contains a long lifetime component, significantly longer than the 12.5 ns laser repetition period (Figure S4).…”

“…Experiments performed on different samples milled by focused ion beam (FIB) show that the implantation of gallium oxide resulting from the FIB process is the major source of background in the horn antenna (Supporting Information Figures S3 and S4). Gallium oxide is luminescent when excited in the UV. , This background contribution can be controlled by FIB while selecting the proper milling depth (Figure S3). Moreover, the gallium oxide luminescence spectrum is shifted toward 400 nm , and can be partially separated from the protein autofluorescence spectra with the 310–360 nm bandpass filter (Figure g).…”

“…Gallium oxide is luminescent when excited in the UV. 50,51 This background contribution can be controlled by FIB while selecting the proper milling depth (Fig. S3).…”

Temperature-dependent Raman-active phonon modes and electron−phonon coupling in β-Ga2O3 microwire

“…In a Raman spectroscopy study of β-Ga 2 O 3 , Dohy et al clarified lattice vibration modes by approximation, and found that the Raman shifts of all peaks exhibit redshifts as the temperature increases. 14) For PL spectroscopy, the origins of emissions in every band have been proposed, [15][16][17][18][19][20] and these origins could be explained by experiments and calculation based on generalized Kohn-Sham theory. [21][22][23] Generally, the UV emission is attributed to the recombination of self-trapping exciton (STE), independent of the doping elements.…”