Undoped Layer Growth for Hole Mobility in Nitride Semiconductors
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Solution Overview
Problem
Existing nitride semiconductor light emitting devices face limitations in enhancing hole injection efficiency due to restricted hole mobility in the p-type semiconductor layer, particularly with the use of undoped layers grown under similar conditions as the hole injection and p-type contact layers, which results in reduced mobility.
Innovation Solution
A light emitting device structure featuring a p-type semiconductor layer with a stack of low concentration doping, undoped, and high concentration doping layers, where the undoped layer is thicker than the sum of the other two and has a dopant concentration less than 2E19/cm^3, and a method for growing this layer via metal organic chemical vapor deposition by controlling gas supply, including blocking H2 gas during undoped layer growth to reduce dopant concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an undoped layer is grown under the same conditions as the hole injection and p-type contact layers, then the layer structure is simplified, but the hole mobility is reduced due to relatively high Mg concentration
Solution Approach 1:
The patent applies local quality by creating distinct regions within the p-type semiconductor layer with different doping concentrations. The undoped layer (33b) is specifically designed with very low Mg concentration (less than 2×10^19/cm³) compared to the low concentration doping layer (33a) and high concentration doping layer (33c). This localized variation in doping quality enables high hole mobility in the undoped region while maintaining overall device functionality.
Solution Approach 2:
The patent changes the doping concentration parameter in the undoped layer to be significantly lower (less than 2×10^19/cm³) than in conventional structures. This parameter change is achieved by controlling Mg source gas supply during MOCVD growth, specifically reducing the flow rate or interrupting Mg source gas during undoped layer formation, thereby improving hole mobility without requiring complex structural modifications.
2Reliability
If the undoped layer thickness is increased to improve hole mobility, then hole injection efficiency is improved, but the overall layer thickness increases
Solution Approach 1:
The patent concentrates the hole mobility enhancement function in a specifically designed undoped layer region with optimized thickness. By creating a localized undoped region (33b) with thickness greater than the sum of doped layers, the patent achieves high hole mobility in the critical injection region without unnecessarily increasing the total p-type layer thickness, as the doped regions (33a and 33c) maintain their necessary functions with minimal thickness.
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 configuration significantly increases hole mobility and injection efficiency, as evidenced by a 10% higher light output in experimental samples, with reduced Mg doping concentration in the undoped layer, thereby improving the overall performance of the light emitting device.
Implementation Method 1
mobility of holes in the hole injection layer is increased to promote movement of holes to be injected into the active layer
Implementation Method 2
a method for growing this layer via metal organic chemical vapor deposition by controlling gas supply
Data Source
Figure 2
AI summary
Provided are a light-emitting element and a method for preparing same. The method includes a method for growing a p-type semiconductor layer having a low-concentration doping layer, an undoped layer and a high-concentration doping layer. During the growth of the low-concentration doping layer and the high-concentration doping layer, both N2 gas and H2 gas are supplied, whereas, during the growth of the undoped layer, the supply of H2 gas is shut off and N2 gas is supplied. Accordingly, the doping concentration of Mg contained in the undoped layer can be further lowered, and thus, hole mobility within the p-type semiconductor layer can be enhanced.