Single-Crystalline All-Oxide α-γ-β Heterostructures for Deep-Ultraviolet Photodetection

Area of Science:

• Materials Science
• Condensed Matter Physics
• Optoelectronics

Background:

• Gallium oxide (Ga₂O₃)-based heterostructures are crucial for power electronics and deep-ultraviolet (DUV) photodetection.
• Previous research focused on Ga₂O₃ on native substrates, limiting conductivity and transparency.
• Transparent conductive oxides (TCOs) are essential for advanced optoelectronic devices.

Purpose of the Study:

• To investigate a novel single-crystalline β-Ga₂O₃ layer grown on an α-Al₂O₃ substrate via an interfacial γ-In₂O₃ layer.
• To develop wafer-scalable, transparent conductive oxide layers with enhanced properties for vertically oriented heterostructures.
• To fabricate and characterize a DUV photodetector based on this all-oxide heterostructure.

Main Methods:

• Growth of single-crystalline β-Ga₂O₃ on α-Al₂O₃ using an intermediate γ-In₂O₃ layer.
• Physical characterization using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), and Rutherford backscattering spectrometry (RBS).
• Determination of energy-band offsets at the β-Ga₂O₃/γ-In₂O₃ interface using X-ray photoelectron spectroscopy (XPS).

Main Results:

• Confirmation of single-crystalline nature and crystallographic orientation relationships among β-Ga₂O₃, γ-In₂O₃, and α-Al₂O₃.
• Identification of a type-II heterojunction at the β-Ga₂O₃/γ-In₂O₃ interface with specific band offsets.
• Fabrication of a DUV photodetector exhibiting high photoresponsivity (94.3 A/W), external quantum efficiency (4.6 × 10⁴%), and specific detectivity (3.09 × 10¹² Jones) at 250 nm.

Conclusions:

• The novel γ-In₂O₃ interfacial layer enables wafer-scalable, single-crystalline Ga₂O₃ heterostructures with excellent properties.
• The developed all-oxide heterostructure is suitable for high-performance vertically oriented optoelectronic devices.
• This work provides a strong foundation for future transparent oxide photonic platforms.