<i>I</i>–<i>V</i> characteristics analysis of planar-type Mg₂Si photodiodes on <i>n</i>-Mg₂Si substrate fabricated by Ag thermal diffusion

Abstract We investigated the current–voltage ( I – V ) characteristics of Mg 2 Si pn-junction photodiodes (PDs) for short-wavelength infrared detection. The Mg 2 Si PDs with a ring electrode were fabricated on n -Mg 2 Si substrates by Ag thermal diffusion and photolithography processes, with two Ag removal processes: all-dry etching (Process A) and partially wet etching (Process B). Temperature-dependent I – V characteristics between 230 and 330 K were analyzed based on the single diode model. Process A exhibited a near-unity ideality factor and lower series resistance, indicating superior junction quality, whereas Process B showed higher series resistance due to contact surface roughening induced by wet etching. Arrhenius analysis and dark current modeling revealed diffusion current dominated at high temperatures, while generation-recombination current became dominant at lower temperatures in both PDs. These findings clarify the influence of Ag removal methods on the electrical performance of Mg 2 Si PDs and provide guidance for optimizing process conditions to achieve low dark current.