CMOS-Compatible Short-Wave Infrared Linear Arrays of Ge-on-Si Avalanche Photodiodes

Abstract

Germanium-containing short-wave infrared (SWIR) avalanche photodiode (APD) arrays on silicon platforms have the potential for monolithic integration into complementary metal-oxide-semiconductor (CMOS) integrated circuits, making them mass-manufacturable, high-performance, arrayed optical detectors operating at wavelengths beyond the silicon cut-off wavelength. Here, the first high-performance, surface-illuminated, 10-pixel linear array of pseudoplanar geometry germanium-on-silicon (Ge-on-Si) APDs operating at 1550 nm wavelength and at temperatures up to 378 K are demonstrated. At room temperature, the dark current, avalanche gain, responsivity, and avalanche breakdown of the devices show good uniformity. Array A exhibits a mean dark current density of 198 ± 62 mA cm⁻² at 90% of the breakdown voltage. The excess noise factor is less than half that of InP-based SWIR APD arrays, which allows Ge-on-Si devices to operate at a higher avalanche gain. A responsivity of 8.2 A W⁻¹ at a gain of 20 and excess noise of 3.3 is achieved when illuminated with 1550 nm wavelength light. The detector array also demonstrates stable performance at 378 K with a maximum avalanche gain of 24. This device architecture will be applicable for the design of large-scale APD arrays on Si platforms for SWIR detection which can be used in imaging, sensing, and optical communication applications.