GaN基底上集成介电薄膜材料的生长方法研究

Study on the Growth of Integrated Dielectric Films on GaN Substrates

将以极化为特征、具有丰富功能特性的介电氧化物材料通过外延薄膜的方式,在半导体GaN上制备介电氧化物/GaN集成薄膜,其多功能一体化与界面耦合效应可推动电子系统单片集成化的进一步发展。然而,由于2类材料物理、化学性质的巨大差异,在GaN上生长介电薄膜会出现严重的相容性生长问题。采用激光分子束外延技术(LMBE),通过弹性应变的TiO2的缓冲层来减小晶格失配度,降低介电薄膜生长温度,控制界面应变释放而产生的失配位错,提高了介电薄膜外延质量;通过低温外延生长MgO阻挡层,形成稳定的氧化物/GaN界面,阻挡后续高温生长产生的扩散反应;最终采用TiO2/MgO组合缓冲层控制介电/GaN集成薄膜生长取向、界面扩散,降低集成薄膜的界面态密度,保护GaN半导体材料的性能。所建立的界面可控的相容性生长方法,为相关集成器件的研发提供了一条可行的新途径。

The integration of multifunctional oxide dielectrics possessing spontaneous polarization with GaN semiconductors can put forward a new direction of developing electronic devices with higher performances. However, dielectric oxides and CaN semiconductors are quite different from each other. It will cause many problems when the two kinds of materials are integrated together. Laser molecular beam epitaxy （LMBE） was used to realize epitaxial growth of dielectric films on GaN substrates. TiO2 template layer was inserted between SrTiO3 dielectric film and GaN to reduce lattice mismatch. It was found that the growth temperature of SrTiO3 films was decreased by 200 ℃ due to similar Ti-O6 octahedron structure between TiO2 and STO. In addition, it was found that the strong ionic characteristics of MgO can lead to the remarkable reduction of the interface diffusion between oxide and GaN. Thus TiOJMgO combined buffer layer was used to realize compatible integrated growth of dielectric/GaN structures which can preserve the semiconductor surface and induce dielectric film epitaxial growth. This new method can provide a practical technique to develop new devices containing dielectrics and GaN.