Optical Semiconductor Device Band Gap Engineering

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Solution Overview

Problem

Semiconductor lasers face limitations in output power due to catastrophic optical damage (COD), which affects their service lifetime and reliability, particularly in high-power applications, and existing solutions struggle to control band gap shifts that impact single-longitudinal-mode lasers like DFB and DBR lasers.

Innovation Solution

The optical semiconductor device features a quantum well active layer with a widened band gap in outer regions near the end surfaces and a controlled band gap in inner regions, achieved through impurity diffusion and vacancy diffusion during a heating process, ensuring minimal variance in band gap across the device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the quantum well active layer uses a uniform band gap structure, then the manufacturing process is simple, but the output power is limited due to catastrophic optical damage (COD)

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidservice lifetime

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The quantum well active layer is designed with different band gap energies in different regions: a first band gap energy in the first region adjacent to the end surface and a second band gap energy in the second region not adjacent to the end surface. This local differentiation allows the structure to have higher resistance to catastrophic optical damage near the end surface while maintaining efficient light emission in the inner region, thereby improving reliability without significantly complicating the manufacturing process.

Inventive Principle:

Principle #3Local quality

2Reliability

If the band gap is widened in outer regions to reduce COD, then the service lifetime is improved, but the band gap shift variance increases affecting laser mode stability

Engineering Contradiction:

Improveservice lifetimeVSAvoidband gap uniformity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent carefully controls the band gap energy parameters in different regions of the quantum well active layer. By setting specific band gap energy ranges for the first region (adjacent to end surface) and second region (inner region), the invention achieves adequate protection against COD while maintaining the single-longitudinal-mode characteristics of DFB and DBR lasers. The parameter optimization ensures that the band gap difference between regions is sufficient to prevent COD but controlled enough to maintain mode stability.

Inventive Principle:

Principle #35Parameter changes

3Power

If the semiconductor laser is designed for high power output, then the output power increases, but catastrophic optical damage occurs more frequently

Engineering Contradiction:

Improveoutput powerVSAvoidservice lifetime

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements a protective structure beforehand by creating a quantum well active layer with higher band gap energy in the region adjacent to the end surface. This structural design anticipates and prevents catastrophic optical damage before it occurs, allowing the laser to operate at high power levels without suffering from COD. The preemptive design enables high power output while maintaining service lifetime.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 effectively reduces COD and maintains the desired band gap shift, enhancing the reliability and output characteristics of single-longitudinal-mode lasers by controlling the band gap in both window and inner regions, thereby improving the service lifetime and reducing yield rate variations.

Implementation Method 1

achieved through impurity diffusion and vacancy diffusion during a heating process

Methodology Applied

Scientific EffectImpurity diffusion: Diffusion

Implementation Method 2

achieved through impurity diffusion and vacancy diffusion during a heating process

Methodology Applied

Scientific EffectVacancy diffusion: Diffusion

Implementation Method 3

achieved through impurity diffusion and vacancy diffusion during a heating process

Methodology Applied

Scientific EffectHeating: Heating

Data Source

PatentUS9225147B2Optical semiconductor device and method of manufacturing the same

Publication Date: 2015.12.29 QD LASER INC

AI summary

An optical semiconductor device includes a semiconductor substrate; a lower cladding layer formed over the semiconductor substrate; a quantum well active layer formed on the lower cladding layer; a diffraction grating layer formed over the quantum well active layer and having diffraction gratings formed in a surface thereof; and an upper cladding layer formed on the diffraction gratings of the diffraction grating layer. Further, a band gap in outer regions of the quantum well active layer that are adjacent to outer end surfaces of the optical semiconductor device is greater than the band gap in an inner region of the quantum well active layer that is located between the outer regions, and a thickness of one or more layers, which include the lower cladding layer and positioned between the semiconductor substrate and the quantum well active layer, is greater than or equal to 2.3 μm.