Characteristics of Ge and SiGe pin Photodiodes without Post-growth Annealing

Abstract

We demonstrate low dark currents Ge pin photodiodes on Si substrate fabricated by UHV-CVD without post-growth annealing and possibility of fabricating any composition SiGe diode between Si0.5Ge0.5 and Ge with as a high responsivity as theoretical calculation even at 0V. SiGe diodes showed diode characteristics like reference Si diodes but had much higher dark currents because of the surface leakage. The Ge diodes had low dark currents but some Ge diodes had high dark currents because of a structural difference. We discuss the difference of the current-voltage characteristics and responsivity between Ge and SiGe and between the Ge diodes with different structure. We also deal with a method to reduce a dark current without post-growth annealing using a Si cap. The photodiodes with low dark current without high temperature annealing is a key to photonics-electronics (P-E) convergence using standard Si processing.