Negative-U system of carbon vacancy in 4H-SiC

Area of Science:

• Materials Science
• Solid-State Physics
• Semiconductor Defects

Background:

• 4H-Silicon Carbide (4H-SiC) is a crucial wide-bandgap semiconductor.
• Understanding intrinsic defects is vital for optimizing 4H-SiC electronic properties.
• The carbon vacancy (V(C)) is a prevalent defect in 4H-SiC.

Purpose of the Study:

• To determine the energy levels and negative-U properties of the carbon vacancy (V(C)) in 4H-SiC.
• To identify the relationship between V(C) and common native defects in 4H-SiC.
• To elucidate the role of V(C) in limiting carrier lifetime and creating deep-level defects.

Main Methods:

• Electron Paramagnetic Resonance (EPR) spectroscopy was employed to probe the electronic structure of defects.
• Deep-Level Transient Spectroscopy (DLTS) was utilized to characterize the electrical properties of defects.
• Combined EPR and DLTS measurements were performed on as-grown 4H-SiC samples.

Main Results:

• The energy levels and negative-U properties of the carbon vacancy (V(C)) in 4H-SiC were successfully determined using EPR.
• The Z(1/2) defect, a known lifetime-limiting defect in 4H-SiC, was identified as the double acceptor level (2-|0) of V(C).
• The EH(7) deep defect in 4H-SiC was attributed to the single donor level (0|+) of V(C).

Conclusions:

• The carbon vacancy (V(C)) in 4H-SiC is directly responsible for the Z(1/2) and EH(7) defects.
• This study clarifies the origin of two major native defects in 4H-SiC, impacting device performance.
• The findings provide a fundamental understanding of V(C) in 4H-SiC, crucial for defect engineering and device optimization.