Orthogonal Photodiode Structure for Long-Wave Sensitivity
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Solution Overview
Problem
Conventional photodiodes with vertical structures face reduced sensitivity in the long-wave range due to decreasing absorption ability, leading to increased operating voltages and inefficient area usage as guard structures occupy photon entry areas, limiting the area efficiency.
Innovation Solution
A photodiode with an orthogonal layer structure is developed, where electrodes and diode layers extend orthogonally to the surface, allowing for a parallel electric field with respect to the photon entry area, decoupling absorption volume and operating voltage, and enabling smaller guard structures that do not obstruct photon detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the absorption volume is increased to improve sensitivity in the long-wave range, then the sensitivity is improved, but the operating voltage must be increased
Solution Approach 1:
The patent transitions from a conventional vertical layer structure to an orthogonal structure where the absorption volume extends laterally rather than vertically. This dimensional change allows the absorption path to be increased without proportionally increasing the operating voltage, as the electric field is applied perpendicular to the photon entry surface while the absorption occurs in the lateral direction.
2Power
If the operating voltage is increased to achieve high electric amplification, then the amplification factor is improved, but the guard structures become larger and occupy more photon entry area
Solution Approach 1:
By changing from vertical to orthogonal structure, the patent allows guard structures to be positioned at the edges of the lateral absorption volume rather than occupying central photon entry areas. The orthogonal arrangement separates the function of photon absorption (lateral) from voltage application (vertical), enabling more efficient use of the photon entry area.
Solution Approach 2:
The orthogonal structure naturally segments the device into distinct functional regions: lateral absorption zones for photon detection and vertical electrode regions for voltage application and guard structure placement. This segmentation allows guard structures to be positioned without obstructing the main photon entry areas.
3Measurement precision
If the absorption path is extended to compensate for sensitivity loss, then the sensitivity is improved, but the device volume must be increased
Solution Approach 1:
The patent extends the absorption path in the lateral dimension rather than increasing vertical depth. This allows achieving long absorption paths suitable for long-wave detection without proportionally increasing the overall device volume, as the lateral extension can be more space-efficient than deep vertical structures.
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 design enhances sensitivity in the long-wave range by maintaining high area efficiency and allowing deeper absorption volumes without increasing operating voltage, preventing undesired breakdowns and improving performance in applications like LIDAR technology.
Implementation Method 1
When absorbing photons in the active region, electron-hole pairs are generated
Implementation Method 2
The diodes are operated in the breakdown region of the reverse direction. When absorbing photons in the active region, electron-hole pairs are generated resulting in an avalanche effect during operation allowing a strong/high/large amplification of the signal
Data Source
AI summary
Embodiments provide a photodiode having two electrodes and an absorption volume for absorbing photons, wherein the absorption volume has a photon entry area, wherein the two electrodes are configured to generate an electric field in an active region between the two electrodes when a reverse voltage is applied, wherein the electric field runs parallel to the photon entry area, wherein, starting from a surface of a semiconductor substrate of the photodiode, the two electrodes essentially extend orthogonally to the surface in a depth direction of the semiconductor substrate, wherein the photodiode has at least one guard structure formed in the semiconductor substrate that is disposed below at least one of the at least two electrodes.