Internal radiation effect on semiconductor β-Ga2O3 crystals grown by the VB Method and anisotropic thermal stress

• Published in: Journal of crystal growth 2024-12, Vol.648, p.127910, Article 127910
• Main Authors: Chayab Draa, Azeddine, Mokhtari, Faiza, Lasloudji, Idir, Zermout, Samir, Lebbou, Kheirreddine
• Format: Article
• Language: English
• Subjects: Crystal anisotropy; Internal radiation; Physics; Thermal stress; Vertical Bridgman; β-Ga2O3 crystal
• ISSN: 0022-0248
• DOI: 10.1016/j.jcrysgro.2024.127910

•The internal radiation effect in both the melt and crystal phases of semiconductor β-Ga2O3 crystals grown using the Vertical Bridgman Method has been numerically analyzed across various growth stages.•The temperature and velocity fields, the position and shape of the solid–liquid interface, and the von Mises stresses have been calculated and analyzed for both opaque and semitransparent cases.•The 3D anisotropic thermal stresses are observed to be greater in the [010] direction, attributed to the higher thermal expansion coefficient in this direction (β22>β11).•Semitransparent β-Ga2O3 crystals are less stressed than opaque ones at all growth stages and therefore they are less likely to crack and could then have good quality. Gallium oxide crystals are semitransparent semiconductors with good optical and electrical properties, which allow their use for several technological applications. During the growth process of β-Ga2O3 crystals, internal radiation plays a crucial role that affects the growth process and then the crystal quality. In this work, the effect of the melt and the crystal transparency on the vertical Bridgman growth of β-Ga2O3 oxide is thoroughly studied. Using a global 2D/3D finite element model, temperature, melt flow, melt-crystal interface, and three-dimensional anisotropic thermal stress are computed at different growth stages. At each stage, four cases are considered, namely, opaque melt and crystal, semi-transparent melt and opaque crystal, semitransparent crystal and opaque melt, and finally semitransparent melt and crystal. The role of internal radiation in each case at different growth stages is then highlighted separately and then coupled together. It was found that the melt-crystal interface is shifted from a convex shape at the early stage to a nearly plane and then to a concave shape at the last stage. The melt flow is then changed from two rolls pattern at the beginning to a single-roll structure at the last stage. Thermal stress of the as-grown ingot is decreased during the growth due to the decrease of temperature non-linearities. Internal radiation inside the crystal acts to increase the melt-crystal interface convexity at the early and middle stages of the growth process and leads to a decrease in its concavity at the final stage. However, the melt transparency leads to the opposite effects, i.e., it decreases the interface convexity at the early stage and increases the interface concavity at the final stage. As a result, fo