Optimization of (3-Ga2O3 photocathode performance based on first-principles calculations

Negative electron affinity (NEA) photocathodes based on (3-Ga2O3 are emerging as transformative candidates for advanced optoelectronic applications. Using first-principles calculations, the surface doping and Cs/O/Cs activation mechanisms was explored to optimize (3-Ga2O3 photocathode performance. Two surface models (A and B) of (3-Ga2O3(100) were compared, with model A demonstrating superior stability, lower work function (WF), and enhanced electronic properties conducive to electron emission. Doping studies revealed that Cu, with the lowest formation energy, significantly reduces the WF upon Cs adsorption, outperforming Zn, Cd, and Mg. The electronic structure analysis highlighted a non-monotonic Fermi level (EF) shift pattern, where dopants transition from donors to acceptors with increasing concentration, and Cd and Zn showed remarkable flexibility in modulating carrier concentrations. Furthermore, simulations of the activation process revealed that the sequence of Cs and O adsorption affects the WF, with direct Cs adsorption achieving the greatest reduction, while preadsorption of O slightly constrained the effects of subsequent Cs adsorption. The alternating Cs/O activation ultimately resulted in a multi-dipole superposition effect and reduced the WF from 7.98 eV to 4.16 eV, demonstrating its efficacy in enhancing photocathode performance. These findings provide critical theoretical insights into the design of next-generation NEA photocathodes.