Magnetoresistive Element With Graded Impurity Concentration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional spin-transport elements face challenges in achieving a high magnetoresistance ratio due to issues like spin attenuation and conductivity mismatch at the interface between ferromagnetic and semiconductor layers, making it difficult to balance low element resistance with high spin output.
Innovation Solution
A magnetoresistive element is designed with a semiconductor channel layer comprising regions of varying impurity concentrations, where high concentrations at the interface with tunnel layers reduce interface resistance and prevent spin attenuation, while a low impurity concentration region allows efficient spin transport, and a gate voltage-controlled region enhances ON/OFF ratio and spin transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the impurity concentration is increased in the semiconductor layer close to the interface with the ferromagnetic layer, then the interface resistance is decreased and conductivity mismatch is solved, but the spin transport property deteriorates and spin output decreases
Solution Approach 1:
The patent applies local quality by creating distinct impurity concentration zones within the semiconductor channel layer. The first region (near the interface) has high impurity concentration (1×10^19 to 1×10^21 atoms/cm³) to reduce interface resistance and Schottky barrier, while the second region (transport region) has low impurity concentration (≤1×10^19 atoms/cm³) to maintain good spin transport property. This spatial variation in impurity concentration allows each region to optimize its local function.
Solution Approach 2:
The semiconductor channel layer is segmented into multiple regions with different impurity concentrations. The patent divides the channel layer into a first region adjacent to the ferromagnetic layer interface, a second region for spin transport, and optionally a third region near the other interface. Each segment serves a specific function: the first region handles interface conductivity, the second region handles spin transport, and the third region manages the opposite interface.
2Reliability
If the element resistance is lowered to improve conductivity, then the spin introduction is easier and speed increases, but the spin transport distance decreases due to increased spin attenuation
Solution Approach 1:
The patent resolves this contradiction by applying local quality with spatially varying impurity concentrations. The first region has high impurity concentration to provide low resistance for spin introduction, while the second region has low impurity concentration to minimize spin attenuation during transport. This allows the element to have both low overall resistance and long spin transport distance.
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 achieves a high magnetoresistance ratio by minimizing spin attenuation and maintaining low element resistance, enabling efficient spin transport and adjustable spin output through gate voltage control.
Implementation Method 1
spin is transported through the semiconductor channel layer from the first ferromagnetic layer to the second ferromagnetic layer
Implementation Method 2
The magnetoresistance effect generated by the spin polarized current flowing between the ferromagnetic electrodes through the nonmagnetic layer is great and thus is referred to as giant magnetoresistance effect (GMR)
Implementation Method 3
This method is used to decrease Schottky barrier generated at the interface between the semiconductor layer and the ferromagnetic layer and to decrease the resistance at the interface
Implementation Method 4
when a maximum value of impurity concentration exists in the side of the semiconductor channel layer from the interface of the semiconductor layer with the ferromagnetic layer, an energy level at which the spin is easy to attenuate will be formed
Data Source
AI summary
The magnetoresistive element includes a semiconductor channel layer, a pinned layer disposed on the semiconductor channel layer via a first tunnel layer, a free layer disposed on the semiconductor channel layer via a second tunnel layer, wherein the semiconductor channel layer includes a first region containing an interface with the first tunnel layer, a second region containing an interface with the second tunnel layer, and a third region, impurity concentrations in the first and second regions are higher than 1×1019 cm−3, an impurity concentration in the third region is 1×1019 cm−3 or less, the first and second regions are separated by the third region, and the impurity concentrations in the first and second regions decrease in the thickness direction of the semiconductor channel layer from the interface between the semiconductor channel layer and the first tunnel layer and the interface between the semiconductor channel layer and the second tunnel layer.