Transparent amorphous oxide semiconductor thin film phosphor, In-Mg-O:Eu

We succeeded in fabricating light-emitting amorphous oxide (LEAO) thin films by doping Eu3+ ions to amorphous In-Mg-O deposited at room temperature using (In, Eu)(2)MgO4 polycrystalline targets by pulsed laser deposition. Clearly visible photoluminescence (PL) with a peak at 615 nm was observed at room temperature by 270 nm light excitation even without post-deposition thermal annealing. The unusual variation of PL intensity with Eu concentration is understood in terms of non-radiative Auger recombination via conduction carriers. The PL intensity also exhibited maximums with respect to oxygen pressure during deposition (PO2) and annealing temperature (T-a), which are explained by recombination centers generated by oxygen deficiency-related defects at low PO2, by excess/weakly-bonded oxygen at high PO2, and by hydrogen depletion at high T-a. Since the LEAO films can be obtained even by room-temperature deposition, it is expected to have flexible optoelectronic applications using plastic substrates. (C) 2016 The Ceramic Society of Japan. All rights reserved

Room-temperature fabrication of light-emitting thin films based on amorphous oxide semiconductor

We propose a light-emitting thin film using an amorphous oxide semiconductor (AOS) because AOS has low defect density even fabricated at room temperature. Eu-doped amorphous In-Ga-Zn-O thin films fabricated at room temperature emitted intense red emission at 614 nm. It is achieved by precise control of oxygen pressure so as to suppress oxygen-deficiency/excess-related defects and free carriers. An electronic structure model is proposed, suggesting that non-radiative process is enhanced mainly by defects near the excited states. AOS would be a promising host for a thin film phosphor applicable to flexible displays as well as to light-emitting transistors

Room-temperature fabrication of light-emitting thin films based on amorphous oxide semiconductor

We propose a light-emitting thin film using an amorphous oxide semiconductor (AOS) because AOS has low defect density even fabricated at room temperature. Eu-doped amorphous In-Ga-Zn-O thin films fabricated at room temperature emitted intense red emission at 614 nm. It is achieved by precise control of oxygen pressure so as to suppress oxygen-deficiency/excess-related defects and free carriers. An electronic structure model is proposed, suggesting that non-radiative process is enhanced mainly by defects near the excited states. AOS would be a promising host for a thin film phosphor applicable to flexible displays as well as to light-emitting transistors. (C) 2016 Author(s)

Ultrawide band gap amorphous oxide semiconductor, Ga-Zn-O

We fabricated amorphous oxide semiconductor films, a-(Ga1-xZnx)O-y, at room temperature on glass, which have widely tunable band gaps (E-g) ranging from 3.47-4.12 eV. The highest electron Hall mobility similar to 7 cm(2) V-1 s(-1) was obtained for E-g = similar to 3.8 eV. Ultraviolet photoemission spectroscopy revealed that the increase in E-g with increasing the Ga content comes mostly from the deepening of the valence band maximum level while the conduction band minimum level remains almost unchanged. These characteristics are explained by their electronic structures. As these films can be fabricated at room temperature on plastic, this achievement extends the applications of flexible electronics to opto-electronic integrated circuits associated with deep ultraviolet region. (C) 2016 Elsevier B.V. All rights reserved

Conversion of an ultra-wide bandgap amorphous oxide insulator to a semiconductor

The variety of semiconductor materials has been extended in various directions, for example, to very wide bandgap materials such as oxide semiconductors as well as to amorphous semiconductors. Crystalline beta- Ga2O3 is known as a transparent conducting oxide with an ultra- wide bandgap of similar to 4.9 eV, but amorphous (a-) Ga2Ox is just an electrical insulator because the combination of an ultra-wide bandgap and an amorphous structure has serious difficulties in attaining electronic conduction. This paper reports semiconducting a-(GaOx)-O-2 thin films deposited on glass at room temperature and their applications to thin-film transistors and Schottky diodes, accomplished by suppressing the formation of charge compensation defects. The film density is the most important parameter, and the film density is increased by enhancing the film growth rate by an order of magnitude. Additionally, as opposed to the cases of conventional oxide semiconductors, an appropriately high oxygen partial pressure must be chosen for a-Ga2Ox to reduce electron traps. These considerations produce semiconducting a-Ga2Ox thin films with an electron Hall mobility of similar to 8 cm(2)V(-1) s (-1), a carrier density Ne of similar to 2x10(14) cm-3 and an ultra-wide bandgap of similar to 4.12 eV. An a-Ga2Ox thin-film transistor exhibited reasonable performance such as a saturation mobility of similar to 1.5 cm(2) V-1 s -1 and an on/ off ratio 4107

Ultrawide band gap amorphous oxide semiconductor, Ga–Zn–O

We fabricated amorphous oxide semiconductor films, a-(Ga1-xZnx)O-y, at room temperature on glass, which have widely tunable band gaps (E-g) ranging from 3.47-4.12 eV. The highest electron Hall mobility similar to 7 cm(2) V-1 s(-1) was obtained for E-g = similar to 3.8 eV. Ultraviolet photoemission spectroscopy revealed that the increase in E-g with increasing the Ga content comes mostly from the deepening of the valence band maximum level while the conduction band minimum level remains almost unchanged. These characteristics are explained by their electronic structures. As these films can be fabricated at room temperature on plastic, this achievement extends the applications of flexible electronics to opto-electronic integrated circuits associated with deep ultraviolet region. (C) 2016 Elsevier B.V. All rights reserved