Modulated Doping in GaN Epitaxial Layers
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Solution Overview
Problem
The fabrication of high-quality and low-resistance epitaxial layers for Group III nitride-based LEDs on silicon carbide substrates is challenging due to increased lattice mismatch and cracking caused by silicon doping, which reduces crystal quality and increases forward voltage.
Innovation Solution
A semiconductor device with a doped Group III nitride region featuring modulated dopant concentrations and delta doped layers, where the dopant concentration is varied in a repeating pattern to reduce cracking and improve crystal quality, is developed. This includes a silicon doped GaN layer with alternating layers of high and low dopant concentrations and delta doped layers at transitions, which are integrated into the epitaxial structure to enhance the performance of the LED.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon doping is increased to reduce resistance and forward voltage, then electrical conductivity is improved, but lattice mismatch increases causing cracks and reducing crystal quality
Solution Approach 1:
The patent divides the doped semiconductor region into multiple intervals with alternating dopant concentrations (high and low). This segmentation allows the structure to benefit from high doping regions (improved conductivity) while using low doping regions to reduce lattice mismatch and prevent cracking, thereby maintaining crystal quality.
Solution Approach 2:
The patent applies different dopant concentrations at different locations within the semiconductor region. High dopant concentrations are applied in specific intervals where electrical conductivity needs improvement, while low dopant concentrations are applied in alternating intervals where lattice mismatch control is critical. This local differentiation resolves the contradiction between conductivity and crystal quality.
2Reliability
If silicon doping is increased to reduce forward voltage, then forward voltage is reduced, but cracking increases due to lattice mismatch
Solution Approach 1:
By segmenting the doped region into alternating high and low dopant concentration intervals, the patent reduces overall cracking while maintaining sufficient doping for low forward voltage. The low doping intervals act as stress-relief zones that prevent crack propagation throughout the entire layer.
Solution Approach 2:
The patent changes the dopant concentration parameter spatially by creating alternating high and low concentration intervals. This parameter modulation allows the structure to achieve low forward voltage (through high doping intervals) while minimizing cracking (through low doping intervals), effectively resolving the contradiction.
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 modulated dopant concentration approach reduces cracking, lowers forward voltage, and improves the crystal quality of the epitaxial layers, resulting in more efficient and robust light emitting diodes with increased silicon dopant concentrations while maintaining high performance.
Implementation Method 1
Doping with silicon, however, may increase lattice mismatch between the silicon doped gallium nitride layer and the silicon carbide growth substrate thereby increasing cracks in the gallium nitride layer
Implementation Method 2
A gallium nitride layer (or other Group III nitride layer), for example, may be doped with an n-type dopant such as silicon to increase majority carrier concentration thereof and thereby reduce a forward voltage through a resulting LED
Data Source
AI summary
A semiconductor device may include a doped semiconductor region wherein a dopant concentration of the semiconductor region is modulated over a plurality of intervals. Each interval may include at least one portion having a relatively low dopant concentration and at least one portion having a relatively high dopant concentration. A plurality of delta doped layers may be included in the plurality of intervals. Related methods are also discussed.