Selective Oxidation on High-Indium-Content InAlAs/InGaAs Metamorphic High-Electron-Mobility Transistors

Up to now, many efforts have been continuously channeled toward the development of oxidation techniques on the III-V compounds for GaAs-based device application, which include thermal oxidation [1-7], chemical anodization [8-12], photochemical oxidation [13-16], plasma oxidation [17-20], Ga2O3 grown by molecular beam epitaxy (MBE) [21-23], Al2O3 grown by atomic layer deposition (ALD) [24], oxidized GaAs or InAlAs prepared by ultraviolet and ozone [25-27], and so on. Although the electrical quality of the GaAs-based MOS structures demonstrated to date is not as good as those obtained from the more mature SiO2/Si system, some of them have yielded promising results for electronic and optoelectronic applications. However, the growth of oxides on the III-V surface is more complex than that on Si. Most of these methods require condensed gases, energy sources (such as excited plasma, electric potential, or optical illumination) or ultrahigh vacuum chamber, and so on, which complicate the oxidation process. In the past years, a technique named liquid phase oxidation (LPO) [28] on GaAs-based materials operated at low temperature (30 oC to 70 oC) has been proposed and investigated. Much progress has been made to form a high-quality oxide on GaAs, for example, the mechanism and kinetics of oxidation [29], fabrication of GaAs MOSFET [30], pre-treatment and post-oxidation annealing of the oxide [31, 32], and GaAs-based devices [33, 34]. The oxidation takes place through the in-diffusion of oxygen at the semiconductor-oxide interface, where a fresh interface at the original semiconductor surface is achieved. This is an easy, economic, and low-temperature method to grow uniform and smooth native oxide films on GaAs-based materials. Utilizing the electroless technique, neither vacuum, gas condensation equipment, nor an assisting energy source is needed. Meanwhile, the technique has potential advantages for electronic and optical device applications due to its 7