Flexible gallium oxide electronics

Abstract

Flexible Ga2O3 devices are becoming increasingly important in the world of electronic products due to their unique properties. As a semiconductor, Ga2O3 has a much higher bandgap, breakdown electric field, and dielectric constant than silicon, making it a great choice for next-generation semiconductor materials. In addition, Ga2O3 is a particularly robust material that can withstand a wide range of temperatures and pressure levels, thus is ideal for harsh environments such as space or extreme temperatures. Finally, its superior electron transport properties enable higher levels of electrical switching speed than traditional semiconducting materials. Endowing Ga2O3-based devices with good mechanical robustness and flexibility is crucial to make them suitable for use in applications such as wearable electronics, implantable electronics, and automotive electronics
However, as a typical ceramic material, Ga2O3 is intrinsically brittle and requires high temperatures for its crystallization. Therefore fabricating flexible Ga2O3 devices is not a straightforward task by directly utilizing the commonly used polymer substrates. In this context, in recent years people have developed several fabrication routes, which are the transfer route, in situ room-temperature amorphous route, and in situ high-temperature epitaxy route. In this review, we discuss the advantages and limitations of each technique and evaluate the opportunities for and challenges in realizing the applications of flexible Ga2O3 devices.

Electrophoretic Deposition of Conformal β-Ga2O3 Films on Arbitrary Substrates for Heterojunction-Based Deep-Ultraviolet Photodetectors

“…The deposition of β-Ga 2 O 3 films on rigid transparent conductive oxide FTO, technologically feasible silicon, insulating glass, flexible aluminum metallic foil, and ITO-PET substrates signifies the key advantage of the simple EPD one-step process to fabricate different novel β-Ga 2 O 3 -based heterojunctions on any type of substrate under ambient conditions. The proposed EPD approach can be extended to deposit β-Ga 2 O 3 polycrystalline films on commercial polymer-based flexible substrates, which currently rely on deposition of amorphous β-Ga 2 O 3 films, due to the limitations of low thermal stability for polymer-based flexible substrates …”

“…The deposition of β-Ga 2 O 3 films on flexible substrates in the literature is demonstrated using (i) mechanical-exfoliation and transfer technique (which lacks reliability and is difficult to scale up for large-scale synthesis), (ii) growth of directly amorphous β-Ga 2 O 3 films on conventional polymer-based flexible substrates (the low thermal stability of conventional polymer substrates hinders the high-temperature crystallization process, affecting the performance of β-Ga 2 O 3 -based devices), and (iii) epitaxially deposited β-Ga 2 O 3 on mica and functionalized Hastealloy substrates at moderate temperatures using expensive vacuum-based methods (<700 °C). 43 Interestingly, the proposed EPD process is used to deposit large area (∼2 cm × 2 cm) β-Ga 2 O 3 films on flexible aluminum metallic foil and ITO-PET substrates at a nominal applied voltage of 120 V for 20 min under ambient conditions. The structural characterization of as-deposited β-Ga 2 O 3 films on flexible aluminum metal foil and ITO-PET substrates reveals the polycrystalline nature, as seen in Figure 3.…”

“…The proposed EPD approach can be extended to deposit β-Ga 2 O 3 polycrystalline films on commercial polymerbased flexible substrates, which currently rely on deposition of amorphous β-Ga 2 O 3 films, due to the limitations of low thermal stability for polymer-based flexible substrates. 43 The as-deposited β-Ga 2 O 3 films on different substrates (FTO, silicon, and Al foil) are further tested for their deep-UV sensing capabilities. The low-cost conductive silver paint is used to make a pair of contacts on top of β-Ga 2 O 3 films and each individual substrate, as depicted in Figure 6a.…”

Experimental Study on Liquid Metal Embrittlement of Al-Zn-Mg Aluminum Alloy (7075): From Macromechanical Property Experiment to Microscopic Characterization

“…The molecular volume of various oxygen-containing gases in the air is large, and the distance between molecules is significantly larger than that of the metal atoms in the liquid metal. Therefore, it is most likely that the oxygen is the result of gallium atoms penetrating the aluminum alloy's interior and being oxidized by the air when exposed to it following the tensile fracture [40].…”

Materials and Structural Designs toward Motion Artifact-Free Bioelectronics

“…Liquid metal is often mentioned as an interesting and promising material that can maintain stable conductivity with a very low modulus. ,,,,,,− Compared to metals with a modulus of GPa, the modulus of a liquid state of a metal can be regarded as near zero. Representative materials include Ga and Ga-based EGaIn and Gallium–Indium–Tin alloys (Gallinstan), − which can maintain conductive liquid properties at room temperature. In addition, due to its nature, a liquid does not require a specific shape or structure to reduce stress.…”