Avalanche Photodiode Buffer Layer Edge Breakdown Suppression
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Solution Overview
Problem
The electron injection-type avalanche photodiode (APD) faces challenges in suppressing edge breakdown due to difficulties in precise control of the doping profile of the n-type region in the embedded n electrode structure, leading to increased avalanche noise and reduced breakdown voltage.
Innovation Solution
A buffer layer with a lower ionization rate is inserted between the n electrode connecting layer and the avalanche multiplication layer, which helps to divert the electric field concentration away from the avalanche multiplication layer, thereby preventing edge breakdown without the need for high-precision doping control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an embedded n electrode structure is used in electron injection-type APD, then the device can achieve high-speed operation and good excess noise characteristics, but edge breakdown occurs due to electric field concentration at the corners of the n-type region
Solution Approach 1:
A buffer layer with low ionization rate is introduced as an intermediary between the n-type region and the avalanche multiplication layer. This buffer layer mediates the electric field distribution, preventing direct concentration of electric field at the corners of the n-type region while maintaining the embedded n electrode structure's high-speed operation benefits.
Solution Approach 2:
The buffer layer is specifically positioned only in regions where electric field concentration occurs (at the corners of the n-type region), providing localized electric field management. This allows different parts of the device to have different properties: the n-type region maintains its embedding structure for high-speed operation, while the buffer layer provides local protection against edge breakdown.
2Reliability
If ion implanted guard ring structure is used to suppress edge breakdown, then breakdown voltage increases, but this structure cannot be formed in electron injection-type APD
Solution Approach 1:
Instead of changing the structural configuration to form a guard ring, the invention changes the material parameter (ionization rate) by introducing a buffer layer with low ionization rate. This parameter change achieves edge breakdown suppression while maintaining the original embedded n electrode structure that is feasible for electron injection-type APD manufacturing.
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 suppresses edge breakdown in electron injection-type APDs using the embedded n electrode structure, enhancing the device's operational stability and noise performance by maintaining a neutral state in the p-type light absorbing layer and adjusting the donor doping to manage electric field changes.
Implementation Method 1
a buffer layer with a low ionization rate is inserted between an n electrode connecting layer and an avalanche multiplication layer
Data Source
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AI summary
An object is to provide an electron injected APD with an embedded n electrode structure in which edge breakdown can be suppressed without controlling the doping profile of an n-type region of the embedded n electrode structure with high precision. In the APD according to the present invention, a buffer layer 33 with a low ionization rate is inserted between an n electrode connecting layer 32 and an avalanche multiplication layer 34. Specifically, the APD is an electron injected APD in which an n electrode layer 31, the n electrode connecting layer 32, the buffer layer 33, the avalanche multiplication layer 34, an electric field control layer 35, a band gap gradient layer 36, a low-concentration light absorbing layer 37a, a p-type light absorbing layer 37b, and a p electrode layer 38 are sequentially stacked, and a light absorbing portion 37 that includes at least the low-concentration light absorbing layer 37a and the p-type light absorbing layer 37b forms a mesa shape.