Zn doping in the In0.53Ga0.47As(100)β2(2 × 4) surface for negative electron affinity photocathode: A first-principles research

InGaAs is an important ternary III-V semiconductor material with good spectral response in the near infrared region of 1-3 μm. The negative electron affinity is generated from the proper sensitization of In0.53Ga0.47As(100)β2(2 × 4) surface. Doping and sensitization are indispensable in the preparation of InGaAs photocathode. However, the surface doping mechanism of InGaAs is not clear. This article focuses on the suitable doping sites of substitutional Zn atoms for sensitization on In0.53Ga0.47As(100)β2(2 × 4) surface. Considering the symmetry, there are eight doping sites and the eight doping surface models are formed. The surface atomic structures and surface formation energies of these models are discussed. The lower the formation energy is, the more stable the surface is. Zn4 and Zn5 are the more stable doping models based on the analysis of formation energy. Therefore the band structure, surface charge distribution, work function and optical properties are further discussed for these two doping models. The Zn4 doping surface has a lower work function and reflectivity and better absorption in the range of 1-3 μm than Zn5. In a word, the InGaAs surface with Zn4 doped is more conducive to the photoelectrons transport and photoemission. Then Zn4 is the most favorable doping site for the InGaAs photocathode.