Progress in MOVPE growth of Ga2O3

Semiconducting sesquioxides, especially Ga2O3, are known since decades [1–3]; however, it is only in the past few years that they are massively investigated. This is essentially due to the development of suitable technologies for growth of large single crystals [4–9] and homo- and heteroepitaxial layers [10–15]. The possibility of growing single crystals and films with relatively low defect density, opened the way to new application areas, in addition to the well-known transparent conducting oxides (TCO) electrodes, namely, (i) substrates for GaN epilayers and (ii) high-power transistors, and (iii) UV detectors. Although the homoepitaxial growth is supposed to provide layers of higher crystallographic perfection, the deposition of gallium oxide on hetero-substrates such as α-Al2O3 (sapphire) is still very popular. It has the advantage of directly providing electrical isolation of the film, which may turn out useful in view of the application of β-Ga2O3 to power field effect transistors (FETs). Furthermore, sapphire wafers are commercially available with diameters of up to 600 and very cheap compared with the still expensive Ga2O3 substrates. This chapter provides a survey of the recent advances in homo- and heteroepitaxial deposition of Ga2O3 by metal-organic vapor-phase epitaxy (MOVPE). This includes (i) MOVPE deposition of β-Ga2O3 on differently oriented β-Ga2O3 homo-substrates; (ii) MOVPE deposition of β-Ga2O3 on hetero-substrates, with special emphasis on sapphire; and (iii) MOVPE deposition of metastable crystalline phases of gallium oxide.