Creation of a Short-Range Ordered Two-Dimensional Electron Gas Channel in Al₂O₃/In₂O₃ Interfaces

The tuning of electrical properties in oxides via surface and interfacial two-dimensional electron gas (2DEG) channels is of great interest, as they reveal the extraordinary transition from insulating or semiconducting characteristics to metallic conduction or superconductivity enabled by the ballistic transport of spatially confined electrons. However, realizing the practical aspects of this exotic phenomenon toward short-range ordered and air-stable 2DEG channels remains a great challenge. At the heterointerface formed after deposition of an Al 2 O 3 layer on a nanocrystalline In 2 O 3 layer, a dramatic improvement in carrier conduction equivalent to metallic conduction is obtained. A conductivity increase by a factor of 10 13 times that in raw In 2 O 3, a sheet resistance of 850 Ω/cm 2, and a room temperature Hall mobility of 20.5 cm 2 V –1 s –1 are obtained, which are impossible to achieve by tuning each layer individually. The physicochemical origin of metallic conduction is mainly ascribed to the 2D interfacially confined O-vacancies and semimetallic nanocrystalline InO x ( x < 2) phases by the clustered self-doping effect caused by O-extraction from In 2 O 3 to the Al 2 O 3 phase during ALD. Unlike other submetallic oxides, this 2D channel is air-stable by complete Al 2 O 3 passivation and thereby promises applicability for implementation in devices.