Bonded SOA-Photodiode Receiver Layout for Lower-Cost Fabrication
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Solution Overview
Problem
The high manufacturing cost of light receiving devices incorporating both photodiodes and semiconductor optical amplifiers is a result of the differing crystal growth conditions required for their compound semiconductor layers, leading to inefficiencies in substrate surface evenness and yield.
Innovation Solution
A light receiving device design where a waveguide semiconductor optical amplifier is formed on one substrate with oblique end faces for input and output light reflection, and a planar photodiode is formed on a separate substrate, allowing for bonding and the use of condenser lenses to optimize light path alignment, thereby reducing manufacturing complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If compound semiconductor layers for semiconductor optical amplifier and photodiode are formed by crystal growth on the same substrate, then integration is achieved, but manufacturing cost increases due to conflicting crystal growth conditions affecting substrate surface evenness and yield
Solution Approach 1:
The invention divides the light receiving device into two separate substrates: a first substrate for the semiconductor optical amplifier and a second substrate for the photodiode. This segmentation allows each component to be manufactured under its optimal crystal growth conditions independently, avoiding the conflict that would arise from attempting to grow both on a single substrate. The separate substrates are then bonded together through back surface bonding, achieving integration without compromising substrate surface evenness or increasing manufacturing cost.
2Ease of manufacture
If compound semiconductor layers for semiconductor optical amplifier and photodiode are formed by crystal growth on the same substrate, then integration is achieved, but manufacturing cost increases due to yield reduction from substrate surface evenness issues
Solution Approach 1:
The invention divides the light receiving device into two separate substrates: a first substrate for the semiconductor optical amplifier and a second substrate for the photodiode. This segmentation allows each component to be manufactured under its optimal crystal growth conditions independently, avoiding the conflict that would arise from attempting to grow both on a single substrate. The separate substrates are then bonded together through back surface bonding, achieving integration without compromising substrate surface evenness or increasing manufacturing cost.
3Speed
If photodiode absorption layer thickness is reduced to increase speed, then carrier travel time decreases, but light receiving sensitivity decreases
Solution Approach 1:
The invention introduces a semiconductor optical amplifier as an intermediary component between the light source and the photodiode. The amplifier compensates for the reduced light receiving sensitivity caused by the thin photodiode absorption layer by providing optical gain. This allows the photodiode to operate with a reduced absorption layer thickness (improving speed) while the amplifier makes up for the sensitivity loss, achieving both high speed and adequate sensitivity in the overall light receiving device.
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 configuration inhibits the increase in manufacturing cost by allowing for separate optimization of semiconductor layer growth conditions for each component and enhances optical coupling tolerance, making the device more cost-effective and efficient.
Implementation Method 1
a first reflection portion formed by an end face at one end of the semiconductor optical amplifier, the end face being formed to be oblique to the principal surface of the first substrate such that input light that is input to a back surface of the first substrate is to be input into the semiconductor optical amplifier; a second reflection portion from which output light is to be output toward the back surface of the first substrate
Implementation Method 2
a planar photodiode formed on a principal surface of the second substrate, the planar photodiode including a light receiving surface
Data Source
Figure 1~2C
Figure 2D~3
AI summary
A light receiving device includes a semiconductor optical amplifier (102) formed on a principal surface (101a) of a first substrate (101). The semiconductor optical amplifier (102) has a first reflection portion (103) that is formed by an end face at one end thereof, the end face being formed to be oblique to the principal surface (101a) of the first substrate (101). The semiconductor optical amplifier (102) also has a second reflection portion (104) that is formed by an end face at the other end thereof, the end face being formed to be oblique to the principal surface (101a) of the first substrate (101). The light receiving device further includes a second substrate (105) having a back surface (105b) bonded to a back surface (101b) of the first substrate (101), and a photodiode (106) formed on a principal surface (105a) of the second substrate (105).