Germanium Photovoltaic Capping Structure for Lower Dark Current
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Solution Overview
Problem
Germanium-containing photovoltaic devices experience high dark current due to interfaces with insulating material layers like silicon nitride, leading to increased background electrical noise and reduced signal-to-noise ratios.
Innovation Solution
Eliminating interfaces between germanium-containing material portions and silicon nitride by embedding germanium in a silicon layer and capping it with a silicon layer or creating a cavity to avoid dielectric material contact, thereby minimizing dark current generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If germanium-containing photovoltaic devices use interfaces with insulating material layers like silicon nitride, then device structure is formed, but dark current increases and signal-to-noise ratio deteriorates
Solution Approach 1:
The patent removes the harmful silicon nitride interface layer from the germanium-containing photovoltaic device structure. By eliminating this specific interface that generates dark current, the invention extracts the harmful element while preserving the functional structure, thereby reducing dark current and improving signal-to-noise ratio
Solution Approach 2:
The patent introduces an intermediate silicon oxide layer between the germanium-containing material and the silicon nitride layer. This intermediary layer prevents direct contact between germanium and silicon nitride, eliminating the harmful interface while maintaining the necessary insulating structure, thus reducing dark current generation
2Object-generated harmful factors
If germanium is embedded in silicon layer and capped with silicon layer or cavity created, then dark current is reduced, but device structure complexity increases
Solution Approach 1:
The patent applies local quality by creating a specific regional structure where germanium is embedded in a silicon layer with a silicon oxide capping layer only in the critical interface region. This localized structural modification addresses the dark current problem at the specific harmful interface without requiring complex changes to the entire device structure
Solution Approach 2:
The patent segments the device structure into distinct functional layers: germanium-containing photovoltaic material layer, silicon oxide capping layer, and silicon nitride insulating layer. This segmentation allows each layer to perform its specific function while preventing harmful interactions, managing complexity through clear structural division
Data Source
AI summary
At least one doped silicon region is formed in a silicon layer of a semiconductor substrate, and a silicon oxide layer is formed over the silicon layer. A germanium-containing material portion is formed in the semiconductor substrate to provide a p-n junction or a p-i-n junction including the germanium-containing material portion and one of the at least one doped silicon region. A capping material layer that is free of germanium is formed over the germanium-containing material portion. A first dielectric material layer is formed over the silicon oxide layer and the capping material layer. The first dielectric material layer includes a mesa region that is raised from the germanium-containing material portion by a thickness of the capping material layer. The capping material layer may be a silicon capping layer, or may be subsequently removed to form a cavity. Dark current is reduced for the germanium-containing material portion.