Nucleation of Threading Dislocations in 4H-SiC at Early Physical-Vapor-Transport Growth Stage

Abstract

In this work, we identify the nucleation mechanism of threading dislocations (TDs) associated with stacking faults (SFs) and 15R-SiC at the early growth stage of 4H-SiC single crystals grown by the physical vapor transport (PVT) technology. By combining molten KOH etching and photochemical etching, we successfully reveal etch pits of TDs and linear etch patterns of SFs on the (112̅0) surface of 4H-SiC single crystals. Systematic investigations based on transmission electron microscopy (TEM) observations and Raman analysis indicate that the Si–C bilayer stacking sequence of SFs is (3, 2) in Zhdanov’s notation. The accumulation of SFs (3, 2) gives rise to the polymorph fluctuation and thus the formation of 15R-SiC at the early PVT growth stage of 4H-SiC single crystals. Quantitative stress analyses indicate that the strain field distributions along the SFs (3, 2) and the 15R-/4H-SiC interfaces are inhomogeneous, which give rise to the nucleation of TDs and low-angle grain boundaries (LAGBs), respectively. The nucleation of LAGBs releases the high stress at the 15R-/4H-SiC interface, which facilities the following 4H-SiC single-crystal growth. Our work indicates that the avoidance of polymorph fluctuation is important to the reduction of TDs at the early growth stage of PVT-grown 4H-SiC single crystals.

Optimization of the process parameters for the AlN crystal growth in the PVT method through an improved numerical simulation considering partial pressure of gas phases

“…However, too high growth rates may introduce defects such as low-angle grain boundaries (LAGBs) and parasitic nucleation during the growth process. 39 The study in ref. 34 indicates that AlN crystals with a low nucleation density, high growth rate (∼100 μm h −1 ), and high quality can be achieved when 0.25 < S < 0.3.…”

Advances and challenges in 4H silicon carbide: defects and impurities

“…For the Frank-type ones, the wave length emitted at 482 nm [115]. By integrating molten KOH with photochemical etching, Shao et al successfully reveal linear etch patterns of SFs located on the (1 1 2 0) surface of crystals [24]. As shown in figure 7(a), the dark-field image contained four linear etch patterns at weak-beam conditions with the diffraction vector of (0330).…”

“…For instance, Kimoto et al identified that carbon vacancies ranged from zero-dimensional point defects can diminish the minority carrier lifetime in 4H-SiC [23]. Furthermore, dislocations, as typical two-dimensional defects in semiconductors, disrupt the material's periodicity, thus affecting the semiconductor's energy levels and local band structure [24]. The existence of dislocation will cause the mechanical properties of 4H-SiC to decline.…”

Effect of subsurface damages in seed crystals on the crystal quality of 4H-SiC single crystals grown by the PVT technology

“…5 It has been proposed that SSDs can be exposed by combining photo-chemical etching and molten-alkali etching. 6,7 However, the effect of SSDs in the seed crystal on the crystal quality of 4H-SiC single crystals is still ambiguous.…”