Single-Photon Avalanche Diode Structure Without Deep Trench Defects

The patent extracts the harmful oxide formation process from the device fabrication by eliminating the deep trench structure that causes oxide pilling. Instead of forming a deep trench and filling it with oxide, the invention uses a planar epitaxial growth approach where the semiconductor layer is grown directly on the substrate surface, removing the source of oxide-related contamination while preserving the detector's functional performance.

The patent inverts the conventional approach by growing the semiconductor material epitaxially on the substrate surface rather than forming structures within a deep trench. This reversal of the fabrication sequence eliminates the need for trench filling and oxide deposition, thereby preventing oxide pilling while still achieving the required device geometry and detection probability through controlled epitaxial layer growth.

The patent removes the deep trench environment from the epitaxial growth process. By performing epitaxial growth on a planar substrate surface rather than inside a deep trench, the invention eliminates the geometric constraints and contamination risks associated with trench-based growth, thereby reducing defect formation and the resulting dark current while still achieving the necessary device structure.

The patent performs preliminary epitaxial growth of the semiconductor layer on the substrate surface before any trench formation or device structuring steps. This preliminary action on a clean, planar surface ensures high-quality crystal growth with minimal defects, and subsequent processing steps can then define the device geometry without compromising the already-formed low-defect semiconductor layer.

The patent merges multiple fabrication steps into a simplified sequence by performing epitaxial growth first to create the semiconductor layer, then using subsequent processing to define device regions. This consolidation eliminates the need for multiple separate mask and dry etch operations that would otherwise be required to create the device structure within a deep trench, reducing overall process complexity while maintaining device performance.

The patent inverts the conventional fabrication sequence by growing the semiconductor material first on a planar surface and then defining device structures through subsequent processing, rather than forming device structures within a deep trench through multiple masks and etches. This inversion simplifies the fabrication process by eliminating redundant steps while preserving the necessary device geometry and performance characteristics.