InP Window Layer Antimony Doping for Low Dark Current Photodetectors
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Solution Overview
Problem
The use of an InGaAs window layer in group III-V compound semiconductor photo detectors increases dark current due to unexpected p-type conductivity in the InP window layer, caused by antimony contamination, leading to expanded p-n junction regions and surface leak currents.
Innovation Solution
Incorporating antimony as an impurity in the InP window layer, with a concentration range of 1×10^17 to 1×10^19 cm^-3, to generate holes that are compensated by n-type dopants, ensuring sufficient n-type conductivity and reducing dark current, and using an undoped InGaAs layer to adjust the anode region's position relative to the absorption layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an InP window layer is used to reduce dark current, then dark current is reduced, but antimony contamination causes p-type conductivity which expands p-n junction region and increases surface leak current
Solution Approach 1:
The patent converts the harmful effect of antimony contamination (which causes p-type conductivity) into a beneficial outcome by intentionally introducing antimony at controlled concentrations (1×10^17 to 1×10^19 cm^-3) to create a transition region. This transition region gradually changes conductivity from p-type to n-type, preventing the formation of expanded p-n junction regions and reducing surface leak current while maintaining low dark current performance.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the antimony concentration in the InP window layer within the range of 1×10^17 to 1×10^19 cm^-3. This parameter control transforms the conductivity profile of the window layer, creating an optimal transition region that eliminates surface leak current without compromising the dark current reduction benefit of using InP instead of InGaAs.
2Use of energy by moving object
If an InGaAs window layer is used, then near-infrared light absorption is improved, but dark current increases due to p-type conductivity
Solution Approach 1:
The patent introduces an undoped InGaAs layer as an intermediary between the InP window layer and the absorption layer. This intermediary layer has intermediate bandgap properties that allow it to transmit near-infrared light effectively while maintaining n-type conductivity, thus preserving light absorption efficiency without introducing the p-type conductivity problem that occurs with InGaAs window layers directly exposed to the surface.
Solution Approach 2:
The patent applies local quality by creating distinct regions with different properties: the InP window layer has controlled antimony concentration for conductivity control, the undoped InGaAs layer provides light transmission, and the absorption layer captures photons. Each layer is optimized for its specific function, allowing the system to achieve both good light absorption and low dark current.
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 reduces dark current by ensuring proper n-type conductivity in the InP window layer and minimizing surface leak currents, while maintaining desired wavelength sensitivity and light-receiving properties.
Implementation Method 1
the InP layer grown on the absorption layer contains antimony as impurity... the n-type dopant contained in the InP layer compensates for the generated carrier
Implementation Method 2
an epitaxial layer stack is grown by metal-organic vapor phase epitaxy
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3(a)~3(b)
AI summary
An object of the present invention is to provide a group III-V compound semiconductor photo detector comprising an absorption layer having a group III-V compound semiconductor layer containing Sb as a group V constituent element, and an n-type InP window layer, resulting in reduced dark current. The InP layer 23 grown on the absorption layer 23 contains antimony as impurity, due to the memory effect with antimony which is supplied during the growth of a GaAsSb layer of the absorption layer 21. In the group III-V compound semiconductor photo detector 11, the InP layer 23 contains antimony as impurity and is doped with silicon as n-type dopant. Although antimony impurities in the InP layer 23 generate holes, the silicon contained in the InP layer 23 compensates for the generated carriers. As a result, the second portion 23d of the InP layer 23 has sufficient n-type conductivity.