Semiconductor Light Emitting Device with GaAs Surface-Controlling Layer
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Solution Overview
Problem
The challenge lies in creating a semiconductor light emitting device with high optical power output and low crystal defect density, as existing methods face difficulties in growing InGaAlP-based layers directly on GaP substrates due to lattice constant mismatch and instability, leading to reduced efficiency and increased absorption of radiant light.
Innovation Solution
A semiconductor light emitting device is developed with a surface-controlling layer made of GaAs, which reduces lattice constant deviation and crystal defects, and a bonding layer that allows for lattice relaxation, enabling the growth of a high-quality upper growth layer on a transparent GaP substrate, thereby enhancing optical power output and reducing absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If InGaAlP-based light emitting layer is grown directly on GaP substrate, then optical power output is improved due to reduced absorption, but crystal defect density increases due to lattice constant mismatch
Solution Approach 1:
A foundation layer comprising a bonding layer and a surface-controlling layer is introduced as an intermediary between the InGaAlP-based light emitting layer and the GaP substrate. The bonding layer (made of GaP, AlP, or InP) bonds to the GaP substrate, while the surface-controlling layer (made of GaAs, InGaAs, or InAlAs) provides a lattice-matched surface for growing the InGaAlP light emitting layer. This intermediary structure reduces lattice constant mismatch and minimizes crystal defect density, enabling high-quality light emitting layers to be grown on GaP substrates for enhanced optical power output.
2Manufacturing precision
If InGaAlP-based light emitting layer is grown on GaAs substrate, then crystal defect density is reduced due to lattice matching, but optical power output decreases due to absorption by the substrate
Solution Approach 1:
The foundation layer is segmented into two distinct functional layers: a bonding layer and a surface-controlling layer. The bonding layer is responsible for bonding to the GaP substrate and is made of materials such as GaP, AlP, or InP. The surface-controlling layer is responsible for providing a lattice-matched surface for growing the InGaAlP light emitting layer and is made of materials such as GaAs, InGaAs, or InAlAs. This segmentation allows each layer to optimize its specific function, enabling both low crystal defect density and high optical power output.
3Strength
If wafer bonding process is performed at high temperature, then bonding strength is improved, but crystal defects increase due to heat treatment influence on light emitting portion
Solution Approach 1:
The foundation layer acts as a protective intermediary that shields the light emitting layer from the high-temperature wafer bonding process. The bonding layer is specifically designed to withstand high-temperature bonding conditions while the surface-controlling layer maintains a stable, lattice-matched surface for the light emitting layer. This protective intermediary structure allows strong bonding to be achieved without degrading the light emitting portion, thus maintaining both bonding strength and low crystal defect density.
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 semiconductor light emitting device with higher optical power output, reduced crystal defects, and improved stability, enabling efficient emission of visual light such as red, orange, yellow, and green, suitable for various applications including lighting and display devices with extended outdoor use and lower power consumption.
Implementation Method 1
bonding a face of the bonding layer and the transparent substrate in a heated state
Implementation Method 2
performing crystal growth of a buffer layer, the surface controlling layer, and the bonding layer, in this order on a first substrate
Data Source
AI summary
A semiconductor light emitting device includes: an upper growth layer including a light emitting layer; a transparent substrate through which a radiant light from the light emitting layer passes; and a foundation layer provided between the upper growth layer and the transparent substrate, the foundation layer having a surface-controlling layer and a bonding layer bonded with the transparent substrate. The surface-controlling layer is made of compound semiconductor including at least Ga and As. The upper growth layer is formed on an upper surface of the surface-controlling layer. A lattice constant difference at an interface between the surface-controlling layer and the upper growth layer is smaller than that at an interface between the bonding layer and the transparent substrate.