Semiconductor Light-Receiving Device Mesa Structure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional semiconductor light-receiving devices face issues with dark current and deterioration due to the exposure of the depletion region, particularly in mesa structures where the dopant diffuses into the light absorption layer, leading to increased dark current and reduced reliability.
Innovation Solution
Incorporating a diffusion buffer layer with a larger band gap than the light absorption layer to prevent the depletion region from being exposed, thereby forming a second mesa with a smaller width that alleviates carrier diffusion and reduces dark current and device capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a mesa structure is formed by removing material around the light-receiving portion, then device capacitance is reduced, but the depletion region becomes exposed in the first mesa surface, increasing dark current
Solution Approach 1:
The patent divides the mesa structure into two distinct levels: a first mesa with a larger diameter and a second mesa with a smaller diameter. This segmentation allows the depletion region to be contained within the first mesa while the second mesa provides additional isolation, thereby reducing dark current without compromising capacitance reduction.
Solution Approach 2:
The patent introduces a vertical dimension to the mesa structure by creating a stepped configuration with two different mesa diameters. This dimensional change allows the depletion region to be strategically positioned and contained, preventing exposure at the smallest mesa surface while maintaining effective capacitance reduction.
2Force
If the depletion region is exposed in the first mesa surface or second mesa top surface, then device capacitance is reduced, but the device deteriorates from the exposed portion, reducing reliability
Solution Approach 1:
The patent segments the mesa structure into two levels where the first mesa contains the depletion region and the second mesa provides an additional protective barrier. This segmentation ensures that the depletion region is not exposed at the smallest mesa surface, preventing deterioration while maintaining effective capacitance reduction through the stepped configuration.
Solution Approach 2:
The patent provides beforehand cushioning by creating a second mesa structure that acts as a protective barrier before deterioration can occur. This additional mesa level prevents direct exposure of the depletion region to environmental factors, thereby protecting the device from deterioration while maintaining the capacitance reduction benefits.
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 approach effectively suppresses dark current and deterioration, enhancing the long-term stability and response speed of semiconductor light-receiving devices while maintaining device reliability.
Implementation Method 1
the dopant used to give conductivity to the conductive semiconductor layer on the surface side thermally diffuses into the light absorption layer
Implementation Method 2
the depletion region occurring in the light absorption layer
Data Source
AI summary
A semiconductor light-receiving device and its manufacturing method are provided which are capable of suppressing dark current and deterioration. Semiconductor crystals were sequentially grown over an n-type InP substrate, including an n-type InP buffer layer, an undoped GaInAs light absorption layer, an undoped InP diffusion buffer layer, and a p-type InP window layer. Next, a first mesa was formed by removing a part from the p-type InP window layer to the n-type InP buffer layer with a Br-based etchant having low etching selectivity, so as to form a sloped “normal” mesa structure. Next, a second mesa having a smaller diameter than the first mesa was formed by dry etching, by precisely removing a part from the p-type InP window layer to a certain mid position of the undoped InP diffusion buffer layer.