Photoluminescence study of β-Ga2O3 nanostructures annealed in different environments

Abstract

β-Ga2O3 nanostructures (nanowires, nanoribbons, and nanosheets) were synthesized via vapor transport method on gold coated silicon substrate in N2 ambient and these β-Ga2O3 nanostructures grown on silicon substrates were taken as the starting material to study the effect of annealing in the different environments (oxygen, water vapour, and ammonia solution) on the structural front and photoluminescence (PL) properties. The PL spectra of β-Ga2O3 nanostructures exhibit a UV-blue emission band whose intensity is strongly affected by the annealing in different environments. Annealing modifies the surface of the nanostructures by creating surface states which quench the PL by creating competitive nonradiative paths. This study also indicates the dominance of the formation of water induced surface states over ammonia induced surface states. The irreversible nature of these defects significantly affects the applicability of this system in moist high temperature environments.

Correlation between surface modification and photoluminescence properties of β-Ga2O3 nanostructures

“…The effect of these parameters on the properties of the device can be studied by optical or electrical methods as the correlation between luminescence and electrical properties in β-Ga 2 O 3 has already been reported. 7,[22][23][24] From our previous studies, it is clear that in β-Ga 2 O 3 nanostructures, UV band intensity is more prone to be affected by surface state trapping centers as compared to blue luminescence. 7,8 This is because, the photo excited electrons which give the UV luminescence, are mobile in the conduction band and get trapped at the surface states.…”

“…7,[22][23][24] From our previous studies, it is clear that in β-Ga 2 O 3 nanostructures, UV band intensity is more prone to be affected by surface state trapping centers as compared to blue luminescence. 7,8 This is because, the photo excited electrons which give the UV luminescence, are mobile in the conduction band and get trapped at the surface states. In contrast to this, in blue luminescence both the electron and the hole are trapped in the donor and acceptor levels respectively and hence are less prone to surface trapping center.…”

“…The techniques, used to grow the nanostructures, have a significant influence on the optical sensing properties. Hence, a comprehensive comparative study of different growth techniques like thermal annealing, 25 thermal evaporation [26][27][28] and Vapor transport method 7,8 have been carried out in this work to study the growth induced factors that affect the oxygen sensing of these nanostructures. The dependence of the PL properties as a function of deposition conditions and synthesis techniques are analyzed to optimize the growth process.…”

“…In contrast to this, in blue luminescence both the electron and the hole are trapped in the donor and acceptor levels respectively and hence are less prone to surface trapping center. 7,8 The luminescence intensity and the intensity ratio of the UV to blue luminescence can be used as an important factor to identify the parameters that can degrade the optical response to oxygen gas. The techniques, used to grow the nanostructures, have a significant influence on the optical sensing properties.…”

“…1,[3][4][5][6][7][8] It has attracted significant attention as a transparent conducting oxide in optoelectronics, 9,10 solar blind photo detectors, 11 optical waveguides 12,13 and host material for phosphors. 13,14 Besides this, β-Ga 2 O 3 nanostructures show good sensing properties with a reversible response to oxygen (O 2 ) and CO gases.…”