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

Abstract

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 β-Ga 2 O 3 is known as a transparent conducting oxide with an ultra-wide bandgap of~4.9 eV, but amorphous (a-) Ga 2 O x 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-Ga 2 O x 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-Ga 2 O x to reduce electron traps. These considerations produce semiconducting a-Ga 2 O x thin films with an electron Hall mobility of~8 cm 2 V − 1 s − 1 , a carrier density N e of~2 × 10 14 cm − 3 and an ultra-wide bandgap of~4.12 eV. An a-Ga 2 O x thin-film transistor exhibited reasonable performance such as a saturation mobility of~1.5 cm 2 V − 1 s − 1 and an on/off ratio 410 7 .

The Feasibility of Using Magnetron Sputtered MoO x as Effective Hole Injection Layer in Organic Light-Emitting Diode

“…It is well acknowledged that the WF of MoO x interlayer plays a key role in governing hole injection characteristics, which can be facilely obtained from the secondary electron cut‐off of UPS measurement. As shown in Figure (a), the cut‐off shifts toward lower binding energy with magnetron sputtered MoO x or thermally‐evaporated MoO x covering onto ITO surface, suggesting an enhanced WF, since the WF is supposed to be the difference between the energy of He I line (21.22 eV) and the calibrated cut‐off value of UPS spectrum . Based on our UPS measurements, the WFs are estimated to be ∼5.2 eV for thermally‐evaporated MoO x and ∼5.3 eV for magnetron sputtered MoO x , which are considerably enhanced as compared with ITO (∼4.8 eV).…”

High Hall Mobility P‐type Cu2SnS3‐Ga2O3 with a High Work Function

“…The schematic of the Cu 2 SnS 3 ‐Ga 2 O 3 structure is shown in Figure a. Crystalline Ga 2 O 3 is known as a conducting oxide with wide band gap, but amorphous Ga 2 O 3 is an insulating material . Therefore, carrier transport takes place through the crystalline Cu 2 SnS 3 as shown in Figure b.…”

Observation of superconductivity in structure-selected Ti2O3 thin films

“…Functional oxides have attracted attention due to their strong structure-property correlation. [1][2][3][4][5][6] For example, enhanced multiferroic properties have been discovered in epitaxial-stabilized tetragonal BiFeO 3 7 and hexagonal TbMnO 3 films, 8 and these structures are absent in the bulk counterparts. Superconductors have zero electrical resistance and magnetic flux expulsion below certain critical temperatures.…”