CdHgTe Semiconductor Barrier Structure for Dark Current Reduction
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Solution Overview
Problem
Semiconductor structures used for detecting electromagnetic radiation face challenges with high dark current noise at low temperatures due to space charge zones, which limits their signal-to-noise ratio, and existing barrier-type structures with doping constraints are difficult to implement industrially.
Innovation Solution
A semiconductor structure with a barrier zone composed of the same elements as the first and second zones, featuring varying constituent element proportions to create a potential barrier only for majority carriers, eliminating the need for doping and reducing interface defects by using cadmium, mercury, and tellurium materials with controlled forbidden band widths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If barrier-type semiconductor structures are used to reduce dark current at low temperature, then dark current is reduced, but interface defects increase due to hetero-structure requirements
Solution Approach 1:
The patent applies homogeneity by using the same semiconductor material (CdHgTe) for all zones including the barrier zone, rather than creating hetero-structures. The barrier is formed by varying the composition ratio of elements within the same material family, ensuring lattice parameter compatibility and eliminating interface defects while maintaining the dark current reduction benefit
Solution Approach 2:
The patent changes the composition parameter (mercury content ratio) of the CdHgTe material to create different zones with different properties. The barrier zone has a specific composition ratio that creates the potential barrier, while other zones have different ratios optimized for their functions, all within the same material system
2Reliability
If doping is used to create potential barriers in barrier zones, then carrier separation is improved, but manufacturing complexity increases due to doping constraints
Solution Approach 1:
The patent extracts the doping step from the manufacturing process entirely. Instead of using doped semiconductor layers, the potential barrier is created purely through composition modulation of the undoped CdHgTe material, simplifying the manufacturing process while achieving the same carrier separation function
Solution Approach 2:
The patent uses composition ratio as a substitute for doping concentration. By varying the mercury content in CdHgTe, the patent achieves the same effect as doping would provide, but through a simpler parameter that can be controlled during material growth without additional doping steps
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
The structure achieves reduced dark current noise and improved signal-to-noise ratio without requiring doping of the barrier zone, maintaining a potential barrier for majority carriers even at high reverse biases, while minimizing interface defects and maintaining sensitivity across a range of operating temperatures.
Implementation Method 1
the barrier zone has a forbidden band adapted to act as a barrier to the majority carriers and to allow the minority carriers to pass. To do this, the barrier zone has a forbidden band width greater than those of the first and of the second zone with an energy difference, between the different zones, that is as small as possible for the energy band corresponding to the minority carriers
Implementation Method 2
Semiconductor structures capable of receiving electromagnetic radiation and transforming it into an electrical signal
Implementation Method 3
when the first zone is reverse-biased, with respect to the second zone, and an electron-hole pair is generated by a photon in the first zone
Implementation Method 4
the minority carrier generated passes from the first zone to the second zone, and is accelerated by the polarization
Implementation Method 5
this is the seat of the current of generation and recombination of electron-hole pairs, of the tunneling current assisted by traps and of the band-to-band tunneling current, which are at the origin of the major part of the current of darkness at low temperature
Data Source
Figure 1~2
Figure 3a~3b
Figure 4
AI summary
The invention relates to a semiconductor structure (5) capable of receiving electromagnetic radiation (lambda) and converting same into an electrical signal comprising first and second areas (20, 60) having the same type of conductivity and consisting of the same elements. The structure further comprises a barrier area (40), which is arranged between the first area and the second area (20, 60) and which is to be used as a barrier to the majority carriers of the first and second areas (20, 60) over a barrier thickness, the smallest band gap width of the barrier area (40) defining a barrier proportion. The structure (5) comprises a first interface area (30) arranged so as to form an interface between the first area (20) and the barrier area (40) over a first interface thickness, the composition of elements of the first interface area varying by a proportion corresponding to that of the first material to the barrier proportion, the first interface thickness being at least equal to half of the barrier thickness.