Wet etching is a simple and effective method to identify defects, fabricate patterns, and polish wafers of semiconductors. We highlight recent progress in wet etching of β-Ga ₂ O ₃ substrates with an aim to comprehensively understand the etching behavior and mechanism.

The effect of an insulation lid on the growth of 4-inch β-Ga₂O₃ single crystals by the Czochralski method is analyzed by numerical simulation. The insulation lid mainly hinders upward radiant heat transfer from the melt and crucible and increases the axial temperature gradient in the crystal. Such benefits make the melt/crystal interface convex, which is conducive to suppressing spiral growth and growing large crystals with high quality. Materials with low thermal conductivity λ and low emissivity ε are the optimal choices for making an insulation lid. The inner hole has a great influence on the isolation of radiant heat, and it is determined that the maximum size of the inner diameter $D_{in}$ should not be larger than 130 mm. Thermal stress analysis results indicated that the insulation lid will cause a better stress distribution, illustrating the effect of the insulation lid on the quality of a cylindrical crystal.

Thermal expansion tensor represents a key parameter for the numerical modeling of the crystal growth process. However, the modeling of β-Ga2O3 commonly utilizes one single thermal expansion constant that misses its anisotropic nature and temperature-dependent characteristics. Herein, we addressed this limitation by calibrating an anisotropic, temperature-dependent thermal expansion tensor using the experimental lattice parameters of β-Ga2O3 up to 1200 K. We found that COMSOL Multiphysics simulations employing the calibrated tensor yield stress distribution remarkably distinct from those relying on the commonly assumed constants. Specifically, our simulations predict a von Mises stress concentration near the crystal bottom, which explains the experimentally observed crack formation at corresponding locations. This contrasts with the simulations using the single-value thermal expansion constant, which fails to predict such stress concentration. The physical origin of crystal cracking is found to be rooted in the compressive force exerted by the iridium crucible during the cooling process. Our findings suggest that the physical anisotropy of β-Ga2O3 should be carefully considered in modeling and simulation. With the calibrated thermal expansion tensor, we provide a validated set of thermomechanical parameters for reliable β-Ga2O3 crystal growth simulations.

Floating particles often appear during the Czochralski (CZ) growth of β-Ga₂O₃ in the Ir crucible, thereby impeding the seeding process. Identifying the floating nanoparticles and then inhibiting or removing them is critical for growing high-quality β-Ga₂O₃ single crystals. We grew β-Ga₂O₃ crystals containing floating particles using the CZ method. It is indicated that the floating particles were composed of Ir with a face-centered cubic (fcc) structure. In addition, the β-Ga₂O₃/Ir interface was comprehensively characterized, showing sharp and straight configuration on the whole with small fluctuations at the nanoscale. Combined with density functional theory (DFT) calculation, we found that Ir-O bonding was responsible for stabilizing the interface. Accordingly, the atomic configuration of the interface with the stablest structure, including the relaxed one, was determined. Based on the formation mechanism of the floating particles, we propose three effective strategies, including blowing sufficient oxygen into the bottom of the Ir crucible, coating a protective layer on its inwall and equipping a mechanical arm for inhibiting or removing them.

The production and application of beta-phase gallium oxide (β-Ga2O3) single crystals—an emerging ultrawide bandgap semiconductor—is frequently coupled with high temperature and mechanical load. Understanding the anisotropic mechanical properties at high temperature is crucial for optimizing the production and application of high-performance β-Ga2O3, enhancing its stability and reliability in high-temperature environments. Selective nanoindentation is conducted on unintentional-doped (100)-grown β-Ga2O3 wafers at both room temperature (RT) and a high temperature (HT) of 600 °C, by aligning one facet of the Berkovich indenter parallel to either [001] or [010] low-index directions in the (100) surface. The [010] direction exhibits higher Young's modulus (E) and lower hardness (H) compared to the [001] direction at RT. The deformation morphology confirmed that the deformed zones were localized under the [001] direction while more homogeneously distributed under the [010] direction. Under HT, both E and H decreased to different extents in both directions, where anisotropic deformation mechanisms were noted. These findings can provide guidance for ultra-precision machining and HT applications of monocrystalline β-Ga2O3.