Resonant Tunneling Diode Oscillator Triple Barrier Quantum Well
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Solution Overview
Problem
Current resonant tunneling diode structures for terahertz wave oscillators face limitations in increasing current density and gain due to thickness constraints of the active layer, leading to high propagation loss and reduced oscillation output.
Innovation Solution
A triple barrier quantum well structure with quantum well layers having a lattice constant different from the substrate and barrier layers with opposite strain, allowing for increased thickness and flexibility in band gap and film thickness settings, enhancing current density and reducing propagation loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the active layer thickness is increased to reduce propagation loss, then propagation loss decreases, but current density and gain cannot be improved due to critical film thickness constraints of strain well structure
Solution Approach 1:
The active layer is segmented into multiple quantum well layers separated by barrier layers. This segmentation allows the total active layer thickness to exceed the critical film thickness of a single strain well layer, enabling reduced propagation loss while maintaining high current density through the distributed structure of multiple thinner well layers.
Solution Approach 2:
The invention transitions from a single-layer strain well structure to a multi-layer quantum well structure with barrier layers in between. This dimensional expansion in the layer stack allows the system to overcome the critical thickness limitation by distributing the strain across multiple interfaces rather than concentrating it in a single thick layer.
2Productivity
If the In composition of InGaAs well layer is increased to improve current density, then current density increases, but film thickness must be reduced due to critical film thickness constraint
Solution Approach 1:
The total well layer thickness is segmented into multiple thinner quantum well layers, each below the critical film thickness. This allows the In composition to be increased in each well layer to improve current density while the segmented structure prevents strain relaxation that would occur in a single thick layer.
Solution Approach 2:
Different regions of the active layer (individual quantum well layers) are designed with high In composition for high current density, while the barrier layers provide strain compensation. This local optimization allows each well layer to operate at maximum In composition without compromising overall structural stability.
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 increases the injection current density, reduces propagation loss, and enhances the generation efficiency of terahertz waves, enabling a high-power, low-power-consumption system for sensing and imaging applications.
Implementation Method 1
carrier transition between sub-bands of the at least two quantum well layers is caused through a photon assist tunnel to generate a gain
Implementation Method 2
The quantum well layers each have a lattice constant different from a lattice constant of a substrate of crystal and are comprised of a layer which has a film thickness smaller than a critical film thickness and has a strain
Data Source
AI summary
An oscillator including a substrate and a resonant tunneling diode including a gain medium provided on the substrate. The gain medium includes at least two quantum well layers and plural barrier layers for separating the quantum well layers from each other. The quantum well layers each have one of a compressive strain and a tensile strain. The plural barrier layers that sandwich the quantum well layers having the strain have a strain in a direction opposite to the direction of the strain of the quantum well layers.