A review of Ga2O3 materials, processing, and devices

Abstract

Gallium oxide (Ga2O3) is emerging as a viable candidate for certain classes of power electronics, solar blind UV photodetectors, solar cells, and sensors with capabilities beyond existing technologies due to its large bandgap. It is usually reported that there are five different polymorphs of Ga2O3, namely, the monoclinic (β-Ga2O3), rhombohedral (α), defective spinel (γ), cubic (δ), or orthorhombic (ε) structures. Of these, the β-polymorph is the stable form under normal conditions and has been the most widely studied and utilized. Since melt growth techniques can be used to grow bulk crystals of β-GaO3, the cost of producing larger area, uniform substrates is potentially lower compared to the vapor growth techniques used to manufacture bulk crystals of GaN and SiC. The performance of technologically important high voltage rectifiers and enhancement-mode Metal-Oxide Field Effect Transistors benefit from the larger critical electric field of β-Ga2O3 relative to either SiC or GaN. However, the absence of clear demonstrations of p-type doping in Ga2O3, which may be a fundamental issue resulting from the band structure, makes it very difficult to simultaneously achieve low turn-on voltages and ultra-high breakdown. The purpose of this review is to summarize recent advances in the growth, processing, and device performance of the most widely studied polymorph, β-Ga2O3. The role of defects and impurities on the transport and optical properties of bulk, epitaxial, and nanostructures material, the difficulty in p-type doping, and the development of processing techniques like etching, contact formation, dielectrics for gate formation, and passivation are discussed. Areas where continued development is needed to fully exploit the properties of Ga2O3 are identified.

An Overview of the Ultrawide Bandgap Ga2O3 Semiconductor-Based Schottky Barrier Diode for Power Electronics Application

“…In consequence, β -Ga 2 O 3 shows a much large Baliga’s figure of merit (BFOM =; ε is the relative dielectric constant, and μ is the electron mobility). BFOM is an important criterion to assess the appropriateness of a material for power device application [3–11]. Table 1 compares the basic physical properties of Si, wide bandgap (GaN, SiC), and ultrawide bandgap ( β -Ga 2 O 3 ) semiconductor material.…”

Structural and Luminescence Properties of Ga2O3:Zn Micro‐ and Nanostructures

“…Several oxide materials, which form the transparent conductive oxide (TCO) family, present very interesting properties for these purposes, such as a wide band gap, reasonable electrical conductivity, and high thermal and chemical stability . Among them, monoclinic Ga 2 O 3 with a bandgap of around 4.8 eV emerges as an excellent candidate for a wide range of applications in which a large bandgap is required . This allows for optoelectronic applications in the whole UV‐vis‐IR range by doping Ga 2 O 3 with optically active ions that present emission at the desired wavelength .…”

Recent Advances in β-Ga2O3–Metal Contacts

“…Hence, to avoid the degradation of contact characteristics at elevated annealing temperature, more complex metal stacks should be adopted. By far, Ti/Al/Au [50, 52], Ti/Au/Ni [61, 62], and Ti/Al/Ni/Au metal stacks [13, 21, 63, 64] have been employed to form electrical contacts on β-Ga 2 O 3 . But a comprehensive comparison of contact characteristics between these metal stacks is still insufficient.…”