MOCVD Tunnel Junction Regrowth for Mg-Activated III-Nitride Layers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for growing tunnel junctions in III-nitride devices using Metal Organic Chemical Vapor Deposition (MOCVD) face challenges due to high resistivity of Mg-doped III-N layers caused by hydrogen passivation and the Mg memory effect, leading to difficult junction formation and reduced device efficiency.
Innovation Solution
The method involves activating p-GaN through in situ or ex situ annealing and using MOCVD to grow a tunnel junction on large III-nitride devices, with techniques like selective area regrowth and mesa etching to re-activate p-GaN layers, and employing delta n-type doping for smoother surfaces and higher carrier concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MOCVD is used to grow tunnel junctions in III-nitride devices, then device efficiency and reliability are improved, but the process becomes difficult to achieve due to high resistivity of Mg-doped layers caused by hydrogen passivation and the Mg memory effect
Solution Approach 1:
The patent applies preliminary action by performing in-situ or ex-situ annealing of the p-GaN layer before tunnel junction regrowth to activate the magnesium dopant and remove hydrogen passivation. This preliminary activation step ensures that the p-GaN is properly prepared for subsequent tunnel junction formation, preventing the high resistivity issue that would otherwise occur during MOCVD growth.
Solution Approach 2:
The patent employs parameter changes by modifying the annealing temperature and atmosphere parameters to optimize hydrogen removal from the Mg-doped p-GaN layer. By controlling the annealing process parameters (temperature, time, atmosphere), the patent achieves proper activation of the p-type dopant while minimizing damage to the underlying structure, thereby enabling successful tunnel junction growth.
2Device complexity
If traditional TCO materials are used for current spreading in III-nitride LEDs, then the structure is simple, but optical losses increase which limits device performance
Solution Approach 1:
The patent applies the taking out principle by removing the traditional transparent conducting oxide (TCO) layer from the device structure and replacing it with an n+-GaN tunnel junction contact. This extraction of the TCO layer eliminates the optical absorption losses associated with these materials while maintaining current spreading functionality through the highly doped n-type GaN layer at the tunnel junction interface.
Solution Approach 2:
The patent uses composite materials by creating a tunnel junction structure that combines highly doped n-type GaN and p-type GaN layers. This composite semiconductor structure provides both electrical functionality (current spreading and injection) and optical transparency, replacing the single-material TCO approach and eliminating optical losses while maintaining structural integrity.
3Productivity
If Mg-doped III-N layers are grown by MOCVD, then the process is compatible with industrial semiconductor processing, but the layers become extremely resistive due to hydrogen passivation
Solution Approach 1:
The patent applies preliminary action by incorporating an annealing step in the MOCVD process sequence that activates the Mg dopant and removes hydrogen passivation before tunnel junction regrowth. This preliminary treatment ensures that the Mg-doped p-GaN layer achieves proper electrical activation while maintaining compatibility with industrial MOCVD processing, preventing the extreme resistivity that would otherwise occur.
Solution Approach 2:
The patent uses an annealing process as an intermediary step between Mg-doping and tunnel junction formation. This intermediary thermal treatment activates the magnesium dopant and removes hydrogen from the p-GaN layer, serving as a bridge that transforms the highly resistive as-grown layer into a conductive layer suitable for tunnel junction operation, while maintaining MOCVD process compatibility.
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 reduces operating voltage and increases efficiency of III-nitride devices, enabling new device structures such as LEDs, power electronics, and solar cells by ensuring full activation of p-GaN layers and improving current spreading.
Implementation Method 1
Metal organic chemical vapor deposition (MOCVD) tools are commonly used in semiconductor processing on an industrial scale
Implementation Method 2
any p-GaN that may be re-passivated by hydrogen at elevated temperatures
Implementation Method 3
reactivated by annealing through the side wall or top surface through diffusion of hydrogen
Data Source
AI summary
A method for fabricating an (Al,Ga,In,B)N or III-nitride semiconductor device, including performing a growth of III-nitride or (Al,Ga,In,B)N material including a p-n junction with an active region and using metal-organic chemical vapor deposition (MOCVD) or chemical vapor deposition; and performing a subsequent regrowth of n-type (Al,Ga,In,B)N or III-nitride material using MOCVD or chemical vapor deposition while utilizing a pulsed delta n-type doping scheme to realize an abrupt, smoother surface of the n-type material and a higher carrier concentration in the n-type material. In another example, the method comprises forming a mesa having a top surface; and activating magnesium in the p-type GaN of the (Al,Ga,In,B)N material through openings in the top surface that expose the p-type GaN's surface. The openings are formed before or after the subsequent regrowth of the tunnel junction.