Exploring Electronic States and Ultrafast Electron Dynamics in AlInP Window Layers The Role of Surface Reconstruction

Abstract

AlInP 001 is widely utilized as a window layer in optoelectronic devices, including world record III V multi junction solar cells and photoelectrochemical PEC cells. The chemical and electronic properties of AlInP 001 depend on its surface reconstruction, which impacts its interaction with electrolytes in PEC applications and passivation layers. This study investigates AlInP 001 surface reconstructions using density functional theory and experimental methods. Phosphorus rich P rich and indium rich In rich AlInP surfaces are prepared with in situ monitoring of the process by reflection anisotropy RA spectroscopy and confirmed by low energy electron diffraction and photoemission spectroscopy. The experimental RA spectra closely match the theoretical predictions obtained by solving the Bethe Salpeter equation. It is shown that missing hydrogen on P rich surfaces and formation of In In 1D atomic chains on In rich surfaces introduce mid gap surface states that pin the Fermi level and induce band bending. Time resolved two photon photoemission measurements reveal ultrafast near surface electron dynamics for both P rich and In rich surfaces, demonstrating photoexcited electrons reaching the surface conduction band minimum and relaxing to mid gap surface states on about hundreds of fs. This work provides the most extensive AlInP surface analysis to date, allowing for more targeted surface and interface engineering, which is crucial for the optimization and design of III V heterostructure