Semiconductor Device Polarization Guard Layers
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Solution Overview
Problem
Hexagonal nitride semiconductor materials exhibit strong electrical polarization fields along the c-axis, leading to reduced efficiency in light emission and band bending effects, which are challenging to mitigate without using exotic substrate materials.
Innovation Solution
A semiconductor device with a layer sequence featuring a core active region surrounded by polarization guard layers made of the same material as the active layer, achieving partial or full shielding of electrical polarization fields through mirror symmetry, allowing natural growth and wider device structure possibilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If hexagonal nitride semiconductor materials are grown with c-axis parallel to substrate surface, then electrical polarization fields are reduced, but exotic substrate materials are required
Solution Approach 1:
The patent introduces polarization guard layers as intermediary elements between the active layer and carrier-confinement layers. These guard layers, made of the same material as the active layer, act as mediators that cancel out polarization fields at the interfaces, allowing the use of conventional c-axis oriented substrates while eliminating the harmful polarization effects.
Solution Approach 2:
The invention extracts and isolates the source of polarization problems by placing dedicated polarization guard layers at specific interfaces. This separates the polarization field generation (at heterointerfaces) from the active region, allowing the active layer to operate without polarization interference while maintaining conventional substrate compatibility.
2Reliability
If strong electrical polarization fields are present, then band bending effects occur, but light emission efficiency is reduced
Solution Approach 1:
The patent applies preliminary anti-action by introducing polarization guard layers that generate opposing polarization fields before charge carriers can be affected by the strong electric fields. These guard layers pre-compensate for the polarization effects, creating a flat-band condition in the active layer that prevents band bending and maintains high light emission efficiency.
3Manufacturing precision
If carrier-confinement layers with larger band gap are used, then quantum confinement is achieved, but polarization field discontinuity increases
Solution Approach 1:
The polarization guard layers serve as intermediary layers between the active layer and carrier-confinement layers. These guard layers have the same material composition as the active layer, creating gradual transitions that reduce polarization field discontinuity while still maintaining effective carrier confinement through the larger band gap of the carrier-confinement layers.
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
The semiconductor device achieves a 'flat-band' situation, increasing the spatial overlap of wave functions and internal quantum efficiency of light emission, reducing the influence of active-layer thickness variations, and enabling sharper optical transitions with reduced wavelength shift.
Implementation Method 1
The active layer is surrounded by a pair of polarization guard layers adjacent to the active region and embedding the active region on opposite sides thereof, both polarization guard layers having the first material composition. The polarization guard layers achieve a partial or full shielding of electrical polarization fields in the active layer.
Implementation Method 2
the active layer and the carrier-confinement layers are configured to effect a quantum-confinement of charge carriers in the active layer in one, two or three spatial dimensions
Implementation Method 3
A reduced overlap in the wave functions of electrons and holes is responsible for a reduced efficiency of light emission in semiconductor light emitter devices based on nitride semiconductors. The semiconductor device achieves a 'flat-band' situation, increasing the spatial overlap of wave functions and internal quantum efficiency of light emission
Data Source
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AI summary
A semiconductor device comprises a layer sequence formed by a plurality of polar single crystalline semiconductor material layers that each have a crystal axis pointing in a direction of crystalline polarity and a stacking direction of the layer sequence. A core layer sequence is formed by an active region made of an active layer stack or a plurality of repetitions of the active layer stack. The active layer stack has an active layer having a first material composition associated with a first band gap energy, and carrier- confinement layers embedding the active layer on at least two opposite sides thereof, having a second material composition associated with a second band gap energy larger than the first band gap energy. A pair of polarization guard layers is arranged adjacent to the active region and embedding the active region on opposite sides thereof. Both polarization guard layers have the first material composition.