Nitride Semiconductor Device Dislocation Reduction via Selective Lateral Growth
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Solution Overview
Problem
Conventional nitride semiconductor laser devices fabricated using selective lateral growth on substrates with mask layers suffer from low production yield and reliability due to defects in the GaN layer, such as dislocations.
Innovation Solution
A process involving the formation of stripe ridges on a nitride semiconductor substrate, followed by selective growth of AlxGayInzN crystals with varying impurity concentrations to form a continuous nitride semiconductor layer, reducing dislocation density and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If selective lateral growth is used to form GaN layer on substrate with mask layer, then laser oscillation can be achieved, but dislocation density increases and reliability decreases
Solution Approach 1:
The invention divides the GaN layer formation into multiple segments: first forming a buffer layer on the substrate, then forming stripe ridges on the buffer layer, and finally performing selective lateral growth on the stripe ridges. This segmentation allows each part to serve a specific function - the buffer layer isolates dislocations from the substrate, the stripe ridges provide controlled growth sites, and the selective growth creates the functional layers with reduced dislocation density.
Solution Approach 2:
The invention introduces intermediate structures between the substrate and the final GaN layer. The buffer layer acts as an intermediary that absorbs and isolates dislocations from the substrate. The stripe ridges serve as intermediate growth sites that enable controlled lateral epitaxial growth. These intermediaries prevent direct contact between the high-dislocation substrate and the functional GaN layers.
2Productivity
If conventional ELO growth is used, then GaN layer can be formed, but production yield decreases due to defects
Solution Approach 1:
The invention applies local quality by creating stripe ridges with specific dimensions and orientations on the buffer layer. The selective lateral growth is performed only on these localized stripe ridge regions, allowing high-quality GaN formation in specific areas while the rest of the substrate serves as a dislocation source that is isolated by the buffer layer. This local approach enables high production yield with reduced defects.
3Reliability
If ridge stripe is formed with narrow width for fundamental mode oscillation, then laser performance improves, but manufacturing complexity increases
Solution Approach 1:
The invention performs preliminary actions by pre-forming the buffer layer and stripe ridges before the selective lateral growth of the GaN layer. The stripe ridges are prepared in advance with the appropriate dimensions and patterns that will later define the laser's oscillation modes. This preliminary structuring simplifies subsequent manufacturing steps and enables precise control of laser performance without increasing overall complexity.
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 results in a nitride semiconductor device with reduced dislocation density, lower operating voltage, and enhanced reliability, suitable for high-yield production of semiconductor lasers for optical disks, displays, and medical applications.
Implementation Method 1
A plurality of stripe ridges are formed on a principal face of a nitride semiconductor substrate. AlxGayInzN crystals (0≦x, y, z≦1: x+y+z=1) are selectively grown on the stripe ridges
Implementation Method 2
the AlxGayInzN crystals containing an n-type impurity at a first concentration; and an Alx′Gay′Inz′N crystal (0≦x′, y′, z′≦1: x′+y′+z′=1) which links every two adjoining AlxGayInzN crystals
Data Source
AI summary
A process for producing a nitride semiconductor according to the present invention includes: step (A) of provided an n-GaN substrate 101; step (B) of forming on the substrate 101 a plurality of stripe ridges having upper faces which are parallel to a principal face of the substrate 101; step (C) of selectively growing AlxGayInzN crystals (0≦x, y, z≦1: x+y+z=1) 104 on the upper faces of the plurality of stripe ridges, the AlxGayInzN crystals containing an n-type impurity at a first concentration; and step (D) of growing an Alx′Gay′Inz′N crystal (0≦x′, y′, z′≦1:x′+y′+z′=1) 106 on the AlxGayInzN crystals 104, the Alx′Gay′Inz′N crystal 106 containing an n-type impurity at a second concentration which is lower than the first concentration, and linking every two adjoining AlxGayInzN crystals 104 with the Alx′Gay′Inz′N crystal 106 to form one nitride semiconductor layer 120.