Photodiode Seed Layer Epitaxy for Dislocation Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Photodiodes face challenges in enhancing photoelectric conversion efficiency due to light signal loss and leakage currents caused by threading dislocations and material differences in the seed and crystalline layers, leading to reduced responsivity and increased dark currents.
Innovation Solution
A photodiode structure is developed with a semiconductor substrate, a crystalline layer, an insulating pattern layer defining holes, a seed layer epitaxially grown within these holes, and a light absorption layer formed on the seed layer, where the seed layer's growth direction is inclined to minimize threading dislocations and enhance light absorption efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional photodiode structure with direct contact between light absorption layer and substrate is used, then manufacturing is simpler, but threading dislocations cause leakage currents and reduced reliability
Solution Approach 1:
The device is segmented into distinct functional layers: a crystalline layer for light transmission, a seed layer for controlled epitaxial growth, and a light absorption layer for photoelectric conversion. This segmentation isolates the light absorption function from the substrate, preventing threading dislocations from causing leakage currents while maintaining manufacturing feasibility through systematic layer fabrication.
Solution Approach 2:
The seed layer acts as an intermediary between the crystalline layer and the light absorption layer. It enables controlled epitaxial growth of the light absorption layer with desired crystal orientation and quality, while preventing direct contact between the light absorption layer and the substrate that would otherwise introduce threading dislocations and leakage paths.
2Reliability
If the light absorption layer is made thicker to improve light absorption, then photoelectric conversion efficiency increases, but threading dislocation density increases causing more leakage
Solution Approach 1:
The seed layer serves as a mediator that enables the growth of a thick light absorption layer while maintaining low threading dislocation density. By providing a controlled nucleation interface with appropriate crystal orientation, the seed layer allows thick film growth necessary for efficient light absorption without propagating threading dislocations from the substrate.
Solution Approach 2:
The crystal orientation parameter of the light absorption layer is controlled through the seed layer to be different from that of the substrate. This parameter change enables thick light absorption layer growth while suppressing threading dislocation formation, as the misoriented growth reduces lattice mismatch accumulation and dislocation propagation.
3Reliability
If material composition is changed to enhance light absorption, then photoelectric conversion improves, but material differences cause interface defects and dark currents
Solution Approach 1:
The seed layer acts as a material transition intermediary between the crystalline layer and the light absorption layer with different composition. It provides a gradual compositional bridge that reduces abrupt interface discontinuities, thereby minimizing interface defects and dark currents while still enabling the light absorption layer to achieve desired photoelectric conversion performance.
Solution Approach 2:
The compositional parameter of the semiconductor layers is changed systematically from the crystalline layer through the seed layer to the light absorption layer. This controlled parameter change enables the light absorption layer to have optimized material composition for high light absorption efficiency while the intermediate seed layer reduces compositional abruptness, minimizing interface defects.
4Ease of manufacture
If the seed layer growth direction is made perpendicular to the substrate for simple fabrication, then manufacturing is easier, but light absorption efficiency is reduced
Solution Approach 1:
The growth direction of the light absorption layer is made dynamic and controllable through the seed layer rather than being fixed perpendicular to the substrate. The seed layer enables the light absorption layer to grow at an optimized angle or orientation that maximizes light absorption efficiency while still being compatible with standard epitaxial fabrication processes, thus maintaining ease of manufacture.
Solution Approach 2:
The growth direction parameter of the light absorption layer is optimized through controlled epitaxial growth on the seed layer. By adjusting the growth conditions and seed layer orientation, the light absorption layer can achieve a growth angle that maximizes optical path length and absorption efficiency, improving photoelectric conversion while remaining manufacturable through established semiconductor fabrication techniques.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces threading dislocation density, increases photoelectric conversion efficiency, and promotes uniform light absorption, leading to improved responsivity and reduced dark currents.
Implementation Method 1
A refractive index of the crystalline layer may be higher than a refractive index of the insulating layer
Implementation Method 2
a seed layer in the plurality of holes and directly on the crystalline layer
Implementation Method 3
a photodiode, which is a photoelectric device configured to convert a light signal into an electric signal
Data Source
AI summary
A photodiode includes a semiconductor substrate, a crystalline layer on the semiconductor substrate, an insulating pattern layer on the crystalline layer to define a plurality of holes exposing a top surface of the crystalline layer, a seed layer in the plurality of holes and directly on the crystalline layer, and a light absorption layer on the seed layer and the insulating pattern layer.