Fabrication and optoelectronic properties of Ga 2 O 3 /Eu epitaxial films on nanoporous GaN distributed Bragg reflectors
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Fabrication and optoelectronic properties of Ga2O3/Eu epitaxial films on nanoporous GaN distributed Bragg reflectors Xiaokun Yang1, Xuejian Du2, Linan He1, Di Wang1, Chongchong Zhao1, Jie Liu1, Jin Ma1, and Hongdi Xiao1,* 1 2
School of Microelectronics, Shandong University, Jinan 250100, China School of Physics and Electronics, Shandong Normal University, Jinan 250100, China
Received: 22 February 2020
ABSTRACT
Accepted: 23 March 2020
Nanoporous GaN distributed Bragg reflectors (DBRs) with a high reflectivity (* 92%), which was fabricated via a doping selective electrochemical etching process, were used to deposit Eu-doped b-Ga2O3 films by using pulsed layer deposition. Structural and chemical composition analyses indicated that the 900 °C-annealed film in air has the best crystalline quality and highest photoluminescence (PL) efficiency. The epitaxial relationship between the b-Ga2O3: Eu film and DBR mirror was Ga2O3 (201)kGaN (0001) with Ga2O3 [010]kGaN [1210]. Compared to the Eu:Ga2O3 film on reference template, the 900 °C-annealed film on the DBR mirror presented a * 20-fold enhancement in the PL emission. The performance enhancement was attributed to light-coupling enhancement of the buried DBR mirror. Because of the good electrical properties of the annealed films, the fabricated DBR substrates pave the way for developing a range of rare-earth-doped Ga2O3 optoelectronic devices.
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
Introduction Gallium oxide (Ga2O3) as a new generation of semiconductors shows the outstanding potential in the optoelectronic devices such as thin film transistor [1, 2], solar-blind photodetector [3, 4], and gas sensor [5, 6], due to its excellent physical and chemical properties such as wide band gap (* 4.9 eV), good physicochemical stability, high breakdown voltage (* 8 MV/cm) and ultraviolet transparency. However, the rare-earth-doped Ga2O3 for light-emitting
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https://doi.org/10.1007/s10853-020-04600-y
devices (LED) has attracted great interest in recent years [7–10]. Initial demonstrations for the LEDs of RE-doped Ga2O3 were europium (Eu)-doped Ga2O3 (Ga2O3/Eu) powders or Ga2O3/Eu film deposited by spray pyrolysis [7, 8]. Subsequently, the pulsed layer deposition (PLD) method was used to fabricate electroluminescent devices with red and green emissions using Eu and erbium (Er)-doped Ga2O3, respectively [9, 10]. Due to the weak luminous efficiency, the LED is difficult to be widely used. According to our knowledge [11–13], therefore, it is
J Mater Sci
necessary to improve internal quantum efficiency (IQE) and light extracting efficiency (LEE) of REdoped Ga2O3 thin films. The IQE enhancement can be achieved by improving the crystalline quality, whereas the LEE enhancement can be realized through implantation of distributed Bragg reflectors (DBRs). Compared to polycrystalline films, single-crystal films have higher IQE. Ga2O3 single-crystal films have been fabricated by metal-organic chemical vapor d
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