Semiconductor Multilayer Reflection Mirror for Light-Emitting Device
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Solution Overview
Problem
Surface-emitting devices, such as light-emitting thyristors, face inefficiencies due to light absorption by the substrate, as only a portion of radiated light is emitted from the uppermost layer, and existing structures struggle to maximize light emission efficiency across a wide range of wavelengths.
Innovation Solution
A light-emitting device structure incorporating a semiconductor multilayer reflection mirror with a partially oxidized DBR and a conductive DBR, which increases reflectivity by optimizing the refractive index difference and provides electrical connection, along with a current confining portion to enhance carrier injection and light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional light-emitting device structure is used, then the device can emit light, but light radiation is isotropic and only a part of the radiated light is emitted from the uppermost layer while light radiated toward the substrate is absorbed by the substrate
Solution Approach 1:
The device is segmented into distinct functional regions: a light-emitting region with the thyristor structure and a reflection region with the DBR mirror. This segmentation directs light emission preferentially upward while reflecting downward radiation back through the emitting layer, reducing substrate absorption losses without requiring complete structural redesign
Solution Approach 2:
A distributed Bragg reflector (DBR) mirror is introduced as an intermediary component between the light-emitting region and the substrate. The DBR mirror mediates the interaction between emitted light and the substrate by reflecting specific wavelength ranges back toward the emission region, thereby reducing energy loss to substrate absorption while maintaining structural feasibility
2Reliability
If the number of pairs in the DBR mirror is increased to improve reflectivity, then reflectivity increases, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The invention optimizes specific parameters of the DBR mirror including the refractive index contrast between high and low refractive index layers, the thickness of each layer (optimized to λ/4 for the target wavelength), and the doping concentration in the semiconductor layers. These parameter optimizations enable achieving high reflectivity with fewer pairs compared to conventional designs with lower parameter optimization
Solution Approach 2:
The DBR mirror uses composite semiconductor material layers with different refractive indices (e.g., AlGaAs and GaAs layers) stacked alternately. This composite structure creates strong optical contrast that enhances reflectivity per pair, allowing high overall reflectivity to be achieved with a reduced number of pairs compared to using single-material mirrors
3Illumination intensity
If a gate voltage and gate current are applied to achieve light emission in the light-emitting thyristor, then light is emitted by recombination of electrons and holes, but the current efficiency is limited by carrier injection efficiency
Solution Approach 1:
The device implements local quality enhancement through a current confining structure that concentrates carrier injection at specific locations (the light-emitting region) rather than distributing it uniformly. The gate electrode and gate current are configured to create localized high-density carrier regions at the junction, improving recombination efficiency and light emission intensity per unit current
Solution Approach 2:
The light-emitting thyristor utilizes dynamic carrier injection controlled by the gate voltage and gate current. By dynamically adjusting the gate parameters, the device can optimize the timing and amount of carrier injection to match the operational requirements, improving overall current efficiency and enabling self-scanning operation in array configurations
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 proposed structure achieves high reflectivity with fewer pairs, improves light emission efficiency by reducing substrate absorption, and allows for high-intensity light emission across a wide range of wavelengths, enhancing the performance of surface-emitting devices like light-emitting thyristors.
Implementation Method 1
a semiconductor multilayer reflection mirror of the first conductivity type, formed on the semiconductor substrate... the semiconductor multilayer reflection mirror includes a first oxidized region which is selectively oxidized and a first conductive region adjacent to the first oxidized region
Implementation Method 2
the first conductive region electrically connects the semiconductor substrate and the first semiconductor layer
Implementation Method 3
the semiconductor multilayer reflection mirror includes a first oxidized region which is selectively oxidized... increases reflectivity by optimizing the refractive index difference
Data Source
AI summary
Provided is a light-emitting device including a semiconductor substrate of a first conductivity type, a semiconductor multilayer reflection mirror of the first conductivity type, formed on the semiconductor substrate, a first semiconductor layer of the first conductivity type, formed on the semiconductor multilayer reflection mirror, a second semiconductor layer of a second conductivity type, formed on the first semiconductor layer, a third semiconductor layer of the first conductivity type, formed on the second semiconductor layer, a fourth semiconductor layer of the second conductivity type, formed on the third semiconductor layer, a first electrode formed on a rear surface of the semiconductor substrate, and a second electrode formed on the fourth semiconductor layer, wherein the semiconductor multilayer reflection mirror includes a first selectively oxidized region and a first conductive region adjacent to the first oxidized region, and the first conductive region electrically connects the semiconductor substrate and the first semiconductor layer.