Infrared Detector Indirect Gap Contact Visible Absorption
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Infrared detectors with PIN diodes, particularly in the SWIR range, face limitations due to the absorption of visible radiation by the lower contact layer, which reduces the incident flux absorbed in the active area, limiting their spectral detection range and efficiency.
Innovation Solution
The use of an indirect gap material for the lower electrical contact instead of the conventional direct gap material to reduce absorption in the visible range, along with a stack of semiconductor layers such as AlAs0.563Sb0.437 or (Al,Ga)AsSb/(Al,Ga)InAs superlattices, which act as an optical window and adapt the conduction bands to minimize overall absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a direct gap material is used for the lower contact layer, then good electrical contact is achieved, but absorption of visible radiation increases
Solution Approach 1:
The patent changes the fundamental parameter of the contact layer material from direct gap to indirect gap semiconductor material. This parameter change fundamentally alters the absorption characteristics, allowing the material to maintain low absorption in the visible range while preserving electrical functionality.
Solution Approach 2:
The patent employs composite material structures, specifically using indirect gap materials or superlattice structures (alternating layers of different semiconductor materials) for the contact layer. These composite structures combine the electrical properties needed for good contact with optical properties that minimize visible radiation absorption.
2Loss of energy
If the thickness of the contact layer is reduced, then visible radiation absorption decreases, but electrical contact quality deteriorates
Solution Approach 1:
By changing the material parameter from direct gap to indirect gap, the patent decouples the relationship between thickness and absorption. The indirect gap material maintains low absorption even at greater thicknesses, allowing sufficient thickness to be used for electrical contact without proportionally increasing visible radiation absorption.
3Reliability
If the contact layer thickness is increased, then electrical contact quality improves, but visible radiation absorption increases
Solution Approach 1:
The patent changes the material parameter from direct gap to indirect gap, which fundamentally alters the absorption coefficient characteristics. This allows the contact layer to be made thicker for improved electrical contact while the indirect gap material inherently maintains lower absorption in the visible range compared to direct gap materials.
4Adaptability or versatility
If conventional direct gap materials are used, then the spectral detection range is limited by substrate and window layer absorption, but using indirect gap materials extends detection to around 0.4 μm
Solution Approach 1:
The patent changes the material parameter from direct gap to indirect gap, which extends the spectral detection range. The indirect gap material's lower absorption coefficient in the visible range allows detection to extend down to around 0.4 μm, significantly expanding the detector's operational spectrum compared to conventional direct gap materials.
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 enhances the quantum efficiency of the infrared detectors by reducing absorption in the visible range, allowing detection up to around 0.4 μm and maintaining performance in the SWIR range, thereby extending the spectral detection range and improving overall detector performance.
Implementation Method 1
The lower contact layer (generally an n-doped semiconductor layer) is a so-called window layer for the SWIR radiation to be detected but absorbs the visible radiation
Implementation Method 2
infrared detectors made up of PIN photodiodes intended for 'SWIR' type infrared detection
Data Source
AI summary
The invention relates to an infrared detector that comprises SWIR semiconducting materials which are sensitive to wavelengths lower than about 2.5 microns, said detector comprising a stack of semiconducting layers containing III-V materials defining a PIN photodiode, said stack including at least: one so-called lower exposed electric contact used as an optical window; and one detection layer sensitive to said wavelengths; characterised in that the so-called lower contact includes at least one pseudomorphic layer of n-doped III-V material(s) with an indirect gap or mesh-adjusted with a substrate used as a transitory substrate that can be made of an InP or GaAs III-V material, or of silicon or germanium.