【Device Papers】Fermi level pinning effect investigation on delafossite CuGaO₂/β-Ga₂O₃ heterojunction: application in UV-photodetectors

      Researchers from Shahid Beheshti University have published a dissertation titled " Fermi level pinning effect investigation on delafossite CuGaO₂/β-Ga₂O₃ heterojunction: application in UV-photodetectors " in Solar Energy.

Abstract

      Defects at the junction are unavoidable and can affect the electronic and optoelectronic properties. Surface states generate a distribution of different energy levels within the energy gap (gap states), which can be charged or uncharged. The charged layer at the interface alters the interface electronic structure, resulting in Fermi level pinning (FLP). We have investigated FLP effect at CuGaO₂/β-Ga₂O₃ junction by taking into account the surface states as well as the various factors such as gap state density (N_gs), gap state energy levels (E_gs), and gap state distribution width (σ_gs). The findings show that when the density of states is up to 3 × 10¹³ cm⁻², the FLP effect is clearly evident, and the band bending variation is reduced. This indicates the gap state parameter (S) of 0.67. At N_gs above 10¹³ cm⁻², surface states have a greater impact and the S parameter declines to less than 0.6. Furthermore, increasing the gap state width intensifies the Fermi level pinning effect, so that broadening above 0.5 eV causes the S parameter to fall below 0.3. As the gap states move away from the valence band edge, FLP effect upsurges. The results verify that the idealized assumptions differ significantly from what actually happens in reality. The simulation of a UV-photodetector (UV-PD) based on the CGO/β-Ga₂O₃ heterojunction demonstrates that considering FLP effects results in a more realistic responsivity of 190 mA/W. Neglecting the FLP conditions yields a responsivity of 219 mA/W, which deviates from real conditions.

DOI：

https://doi.org/10.1016/j.solener.2026.114716