Nitride Semiconductor Device Stress Control Layers

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Solution Overview

Problem

Nitride semiconductor devices face challenges in enhancing light emission efficiency due to thermal stress and lattice stress acting on the active layer, which affects the quality and uniformity of light emission, particularly in high-current, high-output applications.

Innovation Solution

A nitride semiconductor device is designed with a thermal stress control layer and a lattice stress control layer to alleviate these stresses, featuring a material with a smaller thermal expansion coefficient and specific band gap energy, respectively, along with a second layer filling pits in the lattice stress control layer to enhance crystalline properties and reduce current leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a conventional nitride semiconductor structure is used, then the device structure is simple, but thermal stress and lattice stress act on the active layer reducing light emission efficiency

Engineering Contradiction:

Improvelight emission efficiencyVSAvoiddevice structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent segments the stress control function into two distinct layers: a thermal stress control layer (first layer) and a lattice stress control layer (second layer). This segmentation allows each layer to address specific stress types independently, with the thermal stress control layer managing thermal expansion mismatches and the lattice stress control layer managing lattice constant mismatches, thereby improving light emission efficiency without excessive complexity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces intermediary control layers between the n-type nitride semiconductor layer and the active layer. These intermediary layers (thermal stress control layer and lattice stress control layer) act as mediators that buffer and reduce stress transmission to the active layer, preventing direct stress damage while maintaining the overall device structure

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If high current is applied for high-output applications, then output power increases, but thermal stress and lattice stress increase reducing emission uniformity

Engineering Contradiction:

Improveoutput powerVSAvoidemission uniformity

Core Design Contradiction:

PowerVSManufacturing precision

Solution Approach 1:

The patent implements beforehand cushioning by placing thermal stress control layer and lattice stress control layer beneath the active layer before operation. These layers pre-establish stress buffer zones that cushion against thermal and lattice stress during high-current operation, maintaining emission uniformity even when high power is applied

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Object-affected harmful factors

If the thermal stress control layer has high aluminum content to reduce thermal expansion coefficient, then thermal stress control improves, but crystalline quality deteriorates due to pits forming

Engineering Contradiction:

Improvethermal stressVSAvoidcrystalline quality

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent applies taking out by removing defective portions (pits) from the thermal stress control layer through selective etching. This extraction eliminates the harmful crystalline defects while preserving the beneficial low thermal expansion coefficient property of the high-aluminum-content layer, thereby maintaining both thermal stress control and crystalline quality

Inventive Principle:

Principle #2Taking out (Extraction)

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 solution effectively enhances light emission efficiency and uniformity, as demonstrated by improved photoluminescence intensity and emission characteristics, achieving a 12% increase in emission efficiency compared to traditional structures.

Implementation Method 1

a thermal stress control layer disposed between the n-type nitride semiconductor layer and the active layer, and formed of a material having a smaller thermal expansion coefficient than the n-type and p-type nitride semiconductor layers

Methodology Applied

Scientific EffectThermal expansion coefficient difference: Thermal Expansion

Implementation Method 2

the active layer having a lamination of quantum barrier layers and quantum well layers alternated with each other

Methodology Applied

Scientific EffectElectron-hole recombination: Electroluminescence

Implementation Method 3

improved photoluminescence intensity and emission characteristics

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Data Source

PatentUS7973303B2Nitride semiconductor device

Publication Date: 2011.07.05 SAMSUNG ELECTRONICS CO LTD

AI summary

A nitride semiconductor device includes n-type and p-type nitride semiconductor layers, an active layer, the active layer having a lamination of quantum barrier layers and quantum well layers, a thermal stress control layer disposed between the n-type nitride semiconductor layer and the active layer, and formed of a material having a smaller thermal expansion coefficient than the n-type and p-type nitride semiconductor layers, and a lattice stress control layer disposed between the thermal stress control layer and the active layer, and including a first layer and a second layer.