Ga2O3 is emerging as an excellent potential semiconductor for high power and optoelectronic devices. However, the successful development of Ga2O3 in a wide range of applications requires a full understanding of the role and nature of its point and extended defects. In this work, high quality epitaxial Ga2O3 films were grown on sapphire substrates by metal-organic chemical vapor deposition and fully characterized in terms of structural, optical, and electrical properties. Then defects in the films were investigated by a combination of depth-resolved Doppler broadening and lifetime of positron annihilation spectroscopies and thermally stimulated emission (TSE). Positron annihilation techniques can provide information about the nature and concentration of defects in the films, while TSE reveals the energy level of defects in the bandgap. Despite very good structural properties, the films exhibit short positron diffusion length, which is an indication of high defect density and long positron lifetime, a sign for the formation of Ga vacancy related defects and large vacancy clusters. These defects act as deep and shallow traps for charge carriers as revealed from TSE, which explains the reason behind the difficulty of developing conductive Ga2O3 films on non-native substrates. Positron lifetime measurements also show nonuniform distribution of vacancy clusters throughout the film depth. Further, the work investigates the modification of defect nature and properties through thermal treatment in various environments. It demonstrates the sensitivity of Ga2O3 microstructures to the growth and thermal treatment environments and the significant effect of modifying defect structure on the bandgap and optical and electrical properties of Ga2O3.

中文翻译：

---

外延β-Ga2O3薄膜的点缺陷和扩展缺陷

Ga2O3逐渐成为高功率和光电器件的极好的潜在半导体。但是，Ga2O3在广泛应用中的成功开发需要对它的作用和性质以及缺陷的扩展有充分的了解。在这项工作中，通过金属有机化学气相沉积法在蓝宝石衬底上生长了高质量的外延Ga2O3膜，并在结构，光学和电学特性方面进行了充分表征。然后，通过深度分辨多普勒展宽和正电子hil没光谱仪的寿命以及热激发发射（TSE）的组合来研究膜中的缺陷。正电子an没技术可以提供有关薄膜中缺陷性质和浓度的信息，而TSE则可以揭示带隙中缺陷的能级。尽管具有非常好的结构性能，但这些膜仍显示出短的正电子扩散长度，这表明高缺陷密度和长正电子寿命，这是形成与Ga空位有关的缺陷和大空位簇的迹象。正如TSE所揭示的，这些缺陷充当了电荷载流子的深阱和浅阱，这解释了在非本征衬底上形成导电Ga2O3膜之所以困难的原因。正电子寿命测量还显示出整个薄膜深度中空位簇的不均匀分布。此外，该工作研究了在各种环境中通过热处理对缺陷性质和性质的修改。