Avalanche Photodiode Edge Breakdown Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing avalanche photodiode (APD) structures face challenges in reducing dark current and tunnel current due to edge breakdown and electric field concentration, particularly in mesa surface and electrode layer designs, where the InGaAs light absorbing layer is depleted, leading to increased dark current and tunnel current issues.
Innovation Solution
The APD structure incorporates a semi-insulating substrate with a specific laminate constitution including a p-type electrode layer, low impurity concentration light absorbing layer, band gap inclined layer, p-type electric field control layer, avalanche multiplier layer, n-type electric field control layer, and electron transit layer, with a predetermined concentration relationship between the n-type and p-type electric field control layers to manage electric field distribution and depletion regions, reducing edge electric field concentration and dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the InGaAs light absorbing layer is depleted to reduce edge electric field concentration, then edge breakdown is suppressed, but dark current due to InGaAs lateral surface increases
Solution Approach 1:
An undepleted InP buffer layer is introduced as an intermediary between the depleted InGaAs light absorbing layer and the avalanche multiplier layer. This buffer layer has a wider band gap than InGaAs, preventing tunnel current generation while its undepleted state maintains electrical neutrality at the mesa surface, thereby suppressing both edge breakdown and dark current simultaneously
Solution Approach 2:
The invention changes the doping concentration parameter of the buffer layer, setting it to a low concentration range (1×10^16 to 1×10^18 atoms/cm³) that is undepleted under operating conditions. This parameter change allows the buffer layer to maintain electrical neutrality and suppress surface potential effects, reducing dark current while still providing edge field control
2Productivity
If the mesa horizontal dimension is reduced to improve device integration, then device density increases, but dark current due to mesa surface effects increases
Solution Approach 1:
The invention applies different properties to different regions: the InGaAs light absorbing layer is depleted to control edge fields, while the InP buffer layer remains undepleted to maintain electrical neutrality at the mesa surface. This local quality differentiation allows the mesa surface to remain electrically neutral even in small-sized devices, suppressing dark current while enabling high device density
3Reliability
If the n-type electrode layer outer circumference is extended to improve electrical contact, then electrode coverage increases, but edge electric field concentration increases
Solution Approach 1:
The undepleted InP buffer layer serves as a mediator between the n-type electrode layer and the depleted InGaAs light absorbing layer. It provides a transition zone that maintains electrical neutrality and prevents electric field concentration at the electrode edges, allowing extended electrode coverage without increasing edge field stress
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 effectively reduces dark current and tunnel current by controlling the electric field distribution and depletion regions, suppressing edge breakdown and enhancing processing accuracy and device stability, while maintaining high receiver sensitivity.
Implementation Method 1
an avalanche multiplier photodiode (avalanche photodiode: APD) as a highly-sensitive light receiving device
Implementation Method 2
a p-type InGaAs light absorbing layer can be used, the receiver sensitivity is excellent
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
This invention provides an APD which can reduce a dark current derived from a mesa surface and a shape of an electrode layer. An APD 301 is provided with a semi-insulating substrate 1, a first mesa 101 having a first laminate constitution in which a p-type electrode layer 2, a p-type light absorbing layer 3A, a light absorbing layer 3B with a low impurity concentration, a band gap inclined layer 4, a p-type electric field control layer 5, an avalanche multiplier layer 6, an n-type electric field control layer 7A, and an electron transit layer 7B with a low impurity concentration are stacked in this order on a surface of the semi-insulating substrate 1, a second mesa 102 having an outer circumference provided inside an outer circumference of the first mesa 101 as viewed from the laminating direction and having a second laminate constitution in which an n-type electrode buffer layer 8A and an n-type electrode layer 8B are stacked in this order on a surface on the electron transit layer 7B side of the first mesa 101, and in the APD, a total donor concentration of the n-type electric field control layer 7A is lower than a total acceptor concentration of the p-type electric field control layer 5 in a range of 2 × 1011 to 1 × 1012/cm2.