I-V characteristics analysis of planar-type Mg₂Si photodiodes on n-Mg₂Si substrate fabricated by Ag thermal diffusion

We investigated the current-voltage (I-V) characteristics of Mg 2 Si pn-junction photodiodes (PDs) for short-wavelength infrared (SWIR) 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 K 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.