End-face Incident Semiconductor Light Receiving Device L-band Sensitivity
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Solution Overview
Problem
Semiconductor light receiving devices used in optical communications face reduced photosensitivity in the L-band wavelength range due to the upper limit of the InGaAs layer's band gap energy, and existing solutions either increase manufacturing costs or lead to crystal defects when attempting to enhance sensitivity.
Innovation Solution
An end-face incident type semiconductor light receiving device with a first light absorbing region and two reflective sections, where light is reflected and re-entered into the absorbing region multiple times, minimizing light spread and enhancing sensitivity without increasing the absorption region thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the InGaAs layer thickness is increased to improve photosensitivity in the L-band, then light receiving sensitivity is improved, but crystal defects increase and manufacturing cost increases
Solution Approach 1:
The patent introduces a reflective layer on the back surface of the semiconductor substrate to create an optical cavity structure. This transforms the problem from increasing absorption layer thickness (one dimension) to utilizing light reflection and multiple passes through the existing thickness (adding the optical path dimension), thereby improving photosensitivity without increasing physical thickness or crystal defect risk
Solution Approach 2:
The reflective layer causes transmitted light to be reflected back into the light absorbing region, creating multiple passes of light through the InGaAs layer. This continuous interaction between light and the absorbing material enhances photosensitivity without requiring additional material thickness, avoiding the crystal defect problem
2Reliability
If the InGaAs layer thickness is increased to improve photosensitivity in the L-band, then light receiving sensitivity is improved, but manufacturing time and cost increase
Solution Approach 1:
Instead of increasing the physical thickness of the InGaAs layer (which increases manufacturing time), the patent adds a reflective layer on the back surface to create optical recycling. This dimensional change in the optical path allows multiple light passes through the same thickness, improving photosensitivity without extending manufacturing processes
Solution Approach 2:
The patent changes the optical parameters of the system by introducing a reflective layer with specific reflectivity characteristics. This parameter change enables the existing InGaAs layer to interact with light multiple times, achieving enhanced photosensitivity without the need to increase layer thickness or manufacturing complexity
3Reliability
If a surface-incident type structure with reflective portion is used to double the light path, then photosensitivity is improved, but light spread increases and alignment accuracy decreases
Solution Approach 1:
The patent segments the optical interaction into distinct regions: the light absorbing region on the front surface and the reflective layer on the back surface. This segmentation allows controlled light reflection at a specific location, preventing excessive light spread and maintaining alignment accuracy while still achieving multiple light passes for improved photosensitivity
Solution Approach 2:
The patent moves the reflection function from the front surface (same dimension as light entry) to the back surface (opposite dimension). This dimensional change allows light to be reflected back through the absorption region without lateral spread, maintaining precise alignment while achieving enhanced light interaction
4Measurement precision
If a sub-substrate is used to fix the semiconductor substrate surface for surface-incident type devices, then alignment is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent inverts the conventional surface-incident structure by making the back surface the functional side with the reflective layer. This inversion eliminates the need for a sub-substrate to hold the front surface, as the back surface becomes the active optical interface. The result is simplified device structure and reduced manufacturing complexity while maintaining alignment accuracy
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 device improves light receiving sensitivity by allowing light to enter the absorbing region multiple times, effectively doubling the thickness of the absorption area without increasing manufacturing costs or crystal defects, thus enhancing photosensitivity across the L-band and C-band ranges.
Implementation Method 1
a first reflective section for causing light transmitted through the first light absorbing region to enter the first light absorbing region
Implementation Method 2
a single second reflective section for causing the light reflected by the first reflective section and transmitted through the first light absorbing region to reflect directly toward the first light absorbing region
Implementation Method 3
light incident from the end-face of the semiconductor substrate is incident on the first light absorbing region
Data Source
AI summary
The end-face incident type semiconductor light receiving device has a first light absorbing region on the main surface side of the semiconductor substrate and causes light incident from the end-face of the semiconductor substrate to enter the first light absorbing region by reflection or refraction, and the first reflective section is provided on the main surface side of the semiconductor substrate to cause light transmitted through the light absorbing region to enter the first light absorbing region, and a single second reflective section is provided on the back surface for causing the light reflected by the first reflective section and transmitted through the first light absorbing region to reflect directly toward the first light absorbing region.