Defect Engineering and Optoelectronic Properties of Vanadium Doped Semi-Insulating 4H-SiC +

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Vanadium (V) doped semi-insulating 4H-SiC is an ideal material for preparing optical semiconductor switches, nuclear radiation detectors, and quantum light sources due to its ability to achieve Fermi level pinning near the mid bandgap through the amphoteric doping behavior of vanadium, resulting in high resistivity (>10⁹ Ω· cm).

Vanadium replaces silicon sites in 4H-SiC, forming three stable charge states: V³⁺, V⁴⁺, and V⁵⁺, corresponding to the acceptor level, neutral state, and donor level, respectively. The acceptor energy level is located below the conduction band bottom at about 0.8-1.0eV, and the donor energy level is located above the valence band top at about 1.2-1.4eV. This energy level structure gives it excellent compensation ability and can be used to prepare semi-insulating substrates.

1. Energy Level Structure And Charge States of Vanadium in 4H-SiC

According to first principles calculations, the thermodynamic transition energy levels of vanadium in 4H-SiC exhibit significant temperature dependence. Lan et al. found that the V_Si(0/-) acceptor level is shifted down by about 0.07eV at 800K compared to 0K, and the electron capture cross section significantly increases with temperature, reaching about 1000 times the room temperature value at 750K. In addition, considering the inner shell excited states of V⁴⁺ and V³⁺, new transition energy levels such as (0 */-), (0/- *), and (0 */- *) may be introduced, which may correspond to additional DLTS signal peaks in deep level transient spectra.

Fig. 1 Temperature dependent energy levels of (0/-) , V_Si (h) and V_Si(k)

In terms of experiments, Rejhon et al. identified four deep energy levels in the range of 0.68-4.10eV through photocurrent spectroscopy, namely:

E₁=E_c – 0.89eV (V acceptor level, h site),

E₂=E_c-1.1eV (possibly related to V-vacancy complexes),

E₃=E_c-1.5eV (V donor level),

E₄=E_c – 1.7eV (positively charged carbon vacancies).

Fig. 2 Relationship between deep level localization radius and energy level position

2. Impact of Defect Engineering on V⁴⁺ Luminescence Performance

Chakravorty et al. introduced controllable defects into V doped 4H-SiC through 100MeV Ag ion irradiation and systematically studied their effects on V⁴⁺ – related photoluminescence. As the irradiation dose increases, the intensity of the alpha and beta emission lines of V⁴⁺ significantly decreases, while the thermal excitation current increases, indicating that irradiation induced shallow level defects lead to Fermi level depinning and compensation failure. TSC measurements further revealed that defect energy levels with activation energies ranging from 0.20 to 0.42eV appear when the injection volume exceeds 1 × 10¹³ Ag cm⁻². These energy levels participate in the capture and release of charge carriers, directly affecting the semi insulating behavior of the material.

The hot annealing experiment showed that isothermal annealing in the range of 473-1073K can partially restore the resistivity of the sample, but cannot completely eliminate all radiation-induced defects, indicating that high-temperature treatment has limited effect on defect repair and further optimization of the annealing process is needed.

Fig. 3 PL and TSC variation with radiation dose

Fig. 4 Recovery of TSC and resistivity after annealing

3. Photocurrent Characteristics and Hole Trap Effect of V Doped 4H-SiC

Fu et al. found that there was a long tail phenomenon in the photocurrent under 532nm illumination when studying V-compensated 4H-SiC optical switches, while there was no such phenomenon under 1064nm illumination. Through double pulse experiments and transient simulation models, they proposed that this is due to the shallow acceptor level of aluminum acting as a hole trap, capturing and slowly releasing holes, thereby extending the hole lifetime.

Fig. 5 Photocurrent response of different samples under 532nm and 1064nm illumination

The simulation results show that the aluminum energy level is located about 0.21eV above the valence band top, and its capture cross-section is about 2×10⁻¹⁵ cm², which is highly consistent with the parameters of the aluminum acceptor energy level in the literature. In addition, different doping mechanisms (deep donor shallow acceptor DDSA vs shallow donor deep acceptor SDDA) can also affect the competitive capture ability of hole traps, thereby affecting the significance of photocurrent tailing.

4. Temperature Dependence of Deep Energy Levels and Its Significance in Device Simulation

Lan et al. systematically studied the temperature dependence of deep energy levels in V-doped 4H-SiC through first principles calculations combined with I-DLTS experiments. They found that the V (0/-) energy level corresponds to the DLTS peak E1 (activation energy 0.85eV) at 425K, and the E2 peak (activation energy 1.15eV) at 660K, which may be related to the (0*/-) excited state energy level.

In addition, the electron capture cross section increases exponentially with temperature, about 25 times higher at 420K than at 300K, and 568 times higher at 670K. This strong temperature dependence has a significant impact on the carrier recombination behavior of high-power devices at high temperatures, and provides a theoretical basis for simulating optical switches under high temperature or 532nm light excitation conditions.

Fig. 6 Electron capture cross section variation with temperature

It can be seen that V doped semi-insulating 4H-SiC, as a multifunctional semiconductor material, has broad application prospects in fields such as optoelectronic devices, quantum emitters, and power switches.

Whether you need V doped semi-insulating 4H-SiC wafer for research or for industrial applications, please contact us email at [email protected] and [email protected].

 

References:

1. Chakravorty, A., & Kabiraj, D. (2022). Role of Fermi-level depinning in quenching of V4+ related photoluminescence in semi-insulating 4H-SiC. Semiconductor Science and Technology, 37(9), 095024.
2. Lan, Y., Peng, B., Wang, Y., Yuan, H., Hu, J., Dong, L., … & Zhang, Y. (2025). Temperature dependence of deep level positions and capture cross sections in vanadium-doped 4H-SiC. Journal of Applied Physics, 137(17).
3. Rejhon, M., Brynza, M., Grill, R., Belas, E., & Kunc, J. (2021). Investigation of deep levels in semi-insulating vanadium-doped 4H-SiC by photocurrent spectroscopy. Physics Letters A, 405, 127433.
4. Fu, W., Wang, L., Wang, B., Chu, X., Xun, T., & Yang, H. (2022). Investigation on the photocurrent tailof vanadium-compensated 4H–SiC for microwave application. AIP Advances, 12(9).