【Member Papers】Plasmon-Enhanced Performance in Self-Powered Solar-Blind CuCrO₂/β-Ga₂O₃ Heterojunction Photodetectors With Al Nanoparticles

      Researchers from Xiamen University in China have published a dissertation titled "Plasmon-Enhanced Performance in Self-Powered Solar-Blind CuCrO₂/β-Ga₂O₃ Heterojunction Photodetectors With Al Nanoparticles" in the IEEE Sensors Journal.

Project Support

      This work is supported by the National Natural Science Foundation of China under Grant 62171396.

Background

      β-Ga₂O₃ with excellent thermal chemical stability has a large bandgap of around 4.9 eV, which is considered to be the most suitable material to construct self-powered solar-blind photodetectors (PDs). Among self-powered β-Ga₂O₃ PDs with a variety of structures, heterojunction PDs with a higher responsivity (R) and faster response speed become a more commonly used device. This is due to the fact that p-type β-Ga₂O₃ is hard to obtain, and thus, different p-type materials (such as CuCrO₂, etc.) were generally used to realize the heterojunction PDs with n-type β-Ga₂O₃. However, these devices still suffer from relatively low R and low external quantum efficiency (EQE) due to the restrictions of carrier blocking from unideal band alignment, which largely limits their practical applications. As one of the most important classes of plasmonic NPs, Al nanoparticles (NPs) can produce the localized surface plasmon resonance (LSPR) effect and the localized electric field, which is an efficient pathway to improve the performance of the PD owing to its ability to enhance the efficiency of carrier injection. What is more, the combined effect of the LSPR effect and localized electric fields can increase the generation rate and separation speed of photogenerated carriers, which is expected to improve the carrier blocking caused by unideal band alignment, thus overcoming the plight of β-Ga₂O₃-based heterojunction PDs.

Main Content

      The research team demonstrates for the first time the significantly improved performance of self-powered solar-blind CuCrO₂/β-Ga₂O₃ heterojunction PDs by innovatively introducing Al NPs prepared by a facile electron beam evaporation technology with the subsequent high-temperature annealing technique. At a 0 V bias, the dark current of the PD with Al NPs is only 3.67 pA, which is 1.8 times lower than that of the PD without Al NPs with a value of 6.7 pA. The highest R, detectivity (D^*), and EQE are 28.53 mA/W, 2.07 × 10¹² Jones, and 14.0% for the PD without Al NPs, while 0.82 A/W, 8.09 × 10¹³ Jones, and 402.8% for the PD with Al NPs, exhibiting an increase by 28.9, 39, and 28.9 times, respectively. Obviously, R, D^*, and EQE are significantly improved in CuCrO₂/β-Ga₂O₃ PDs with Al NPs, which outperform most reported β-Ga₂O₃-based heterojunction PDs. The improvement mechanism on the performance of the CuCrO₂/β-Ga₂O₃ PD with Al NPs can be attributed to the following: under the 254 nm illumination, the LSPR effect and the localized electric field produced by Al NPs improve the efficiency of hole injection. Moreover, the combined effect of the LSPR effect and localized electric fields can not only accelerate the generation rate of photogenerated carriers but also improve the separation speed of photogenerated carriers. The above effects arising from the LSPR effect and localized electric fields contribute to a larger photocurrent, resulting in the improvement of the performance of the PD.

Conclusion

      High-performance self-powered solar-blind CuCrO₂/β-Ga₂O₃ heterojunction PDs with Al NPs obtained by a facile electron beam evaporation with a consequent high-temperature annealing process are fabricated and investigated. Compared with the CuCrO₂/β-Ga₂O₃ PD without Al NPs, the R, D^*, and EQE of the CuCrO₂/β-Ga₂O₃ PD with Al NPs are greatly improved by 28.9, 39, and 28.9 times, respectively. These PDs exhibit a low dark current of 3.67 pA, a high R of 0.82 A/W, a high D^* of 8.09 × 10¹³ Jones, and a high EQE of 402.8%, which can be compared favorably with that of most reported β-Ga₂O₃-based heterojunction PDs. Such brilliant performances could be attributed to the localized electric field and the LSPR effect produced by the Al NPs, which is conducive to enhancing the efficiency of hole injection and increasing the generation rate and separation speed of photogenerated carriers. This study suggests that using Al NPs to modify the surface of the device is an effective and easy-to-controlled method to improve the performance of solar-blind PDs.