Optoelectronic Properties of In[sub.0.87]Ga[sub.0.13]As[sub.0.25]P[sub.0.75] Surface: A First-Principles Study

InGaAsP photocathode surface affects the absorption, transport and escape of photons, and has a great influence on quantum efficiency. In order to study InGaAsP photocathode surface, the electronic structure, work function, formation energy, Mulliken population and optical properties of In[sub.0.87]Ga[sub.0.13]As[sub.0.25]P[sub.0.75](001)β[sub.2](2×4) reconstruction surface were calculated from first principles. Results show that stabilized the In[sub.0.87]Ga[sub.0.13]As[sub.0.25]P[sub.0.75](001)β[sub.2](2×4) surface is conducive to the escape of low-energy photoelectrons. The narrow bandgap and emerging energy levels of the reconstruction surface make the electron transition easier. Under the action of the dipole moment, the electrons transfer from inner layers to the surface during the surface formation process. By contrast to the bulk, the surface absorption coefficient and reflectivity considerably decrease, and the high-reflection range becomes narrower as the falling edge redshifts. On the contrary, the surface transmissivity increases, which is conducive for the photons passing through the surface into the bulk to excite more photoelectrons. Meanwhile, the higher absorption coefficient of surface in low-energy side is favorable for long-wave absorption. The dielectric function peaks of the surface move toward the low-energy side and peak values decrease.