THz Rectifier Double Metallurgical Junction Asymmetric Depletion
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Solution Overview
Problem
Current rectifiers for THz band radiation sensors face challenges in generating significant electric current due to high potential barriers and large depletion zones, requiring substantial potential differences that are not realistically achievable with available sources.
Innovation Solution
A rectifier with a semiconductor substrate and double metallurgical junctions, comprising first and second depletion zones with asymmetric deformation, allowing for the generation of continuous electric current even with reduced potential differences, by adjusting the doping concentrations and work function of the metal end surface to optimize potential barriers and electric field interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a p-n semiconductor junction is used as a rectifier, then the structure is simple and easy to manufacture, but the potential barriers are high (0.5V-0.7V) requiring substantial potential differences that are not realistically achievable
Solution Approach 1:
The rectifier is segmented into multiple sections (first section with n-type layer and first metallurgical junction, second section with p-type layer and second metallurgical junction) connected in series. This segmentation allows the total potential barrier to be distributed across multiple smaller barriers, reducing the potential difference required at each individual junction while maintaining the overall rectification function.
Solution Approach 2:
The patent employs asymmetric doping concentrations in the semiconductor layers, with the first n-type layer having a different doping concentration than the second p-type layer. This asymmetry creates unequal potential barriers at the two metallurgical junctions, optimizing the rectification efficiency while reducing the total potential difference requirement compared to symmetric designs.
2Device complexity
If a p-n semiconductor junction is used as a rectifier, then the structure is simple, but the depletion zones are large causing crossing times by charge carriers to be higher than the period of the electromagnetic radiation
Solution Approach 1:
The depletion zones are segmented into multiple smaller zones distributed across the series-connected metallurgical junctions. This segmentation reduces the width of each individual depletion zone, allowing charge carriers to cross each zone more quickly (within the electromagnetic radiation period) while the series connection maintains the overall rectification capability.
Solution Approach 2:
The patent transitions from a single-plane depletion zone structure to a multi-layered structure with depletion zones distributed across different spatial dimensions (multiple semiconductor layers). This dimensional change allows the total depletion width to be spread out, reducing the crossing time through any single depletion zone while maintaining the cumulative rectification effect.
3Volume of moving object
If a metal-oxide-semiconductor structure is used with reduced oxide thickness (2nm-5nm), then the structure is more compact, but a significant potential difference of the order of magnitude of the Volt is still required
Solution Approach 1:
The rectification function is segmented across multiple metallurgical junctions in series, each contributing a portion of the total potential barrier. This segmentation allows the use of thinner oxide layers (reducing volume) while distributing the potential difference requirement across multiple junctions, avoiding the need for a single high-potential-difference interface.
Solution Approach 2:
The patent employs a composite structure combining metal layers, oxide layers, and semiconductor layers with different doping types (n-type and p-type). This composite material approach allows optimization of each layer's thickness and properties, achieving compact dimensions with reduced oxide thickness while maintaining appropriate potential barriers through the combined effect of multiple interfaces.
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 solution enables the generation of continuous electric current with a mean value different from zero, even under periodic electromagnetic signals, enhancing the efficiency of THz band radiation detection by optimizing the rectification process through asymmetric depletion zone manipulation.
Implementation Method 1
The electromagnetic radiation induces an electromotive force in the antenna and an electric current, oscillating at the same frequency of the electromagnetic radiation
Implementation Method 2
Positioning a non-linear electronic element between the contacts of the air gap, the presence of a variable voltage to the frequency of the electromagnetic radiation, and therefore the presence of a variable electric field, produces a passage of electrical charge in a preferential direction
Implementation Method 3
The presence of a capacity, suitably sized, in series with said non-linear electronic element produces an accumulation of such electrical charge, and consequently the establishment of a potential difference
Data Source
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Figure 3
Figure 4~5
AI summary
The present invention relates to a rectifier for a sensor of electromagnetic signal, said electromagnetic signal having a frequency between 300Ghz and 10THz. Said rectifier comprising: - a semiconductor substrate (1 ) doped p/n comprising a electrons/holes gathering well (2) for gathering electrons/holes; said electrons/holes gathering well (2) being arranged inside said semiconductor substrate (1 ) and comprising at least a first zone doped n/p (21 ); said first zone doped n/p (21 ) having an end surface (21 A); - a metal end surface (41 ) of an antenna (4), said antenna being capable of receiving and concentrating said electromagnetic signal; - a layer doped p/n (3) having a first surface (31) and a second surface (32), opposite to said first surface (31 ). In particular, a first portion of said first surface (31) of said layer doped p/n (3) is in contact with said end surface (21 A) of said first zone doped n/p (21 ) of the electrons/holes gathering well (2), so as to form a first metallurgical junction (G1 ), and a first portion of said second surface (32) of said layer doped p/n (3) is in contact with said metal end surface (41 ), so as to form a second metallurgical junction (G2). The concentration of the doping of said layer doped p/n (3) and the concentration of the doping of said first zone doped n/p (21) of said electrons/holes gathering well (2) are such that said first metallurgical junction (G1) has a first potential barrier (VZ1) inside and the work function of the metal of said metal end surface (41 ) is selected such that it is equal to that of a semiconductor doped n/p and such that said second metallurgical junction (G2) has a second potential barrier (Vzz) inside. Said first metallurgical junction (G1 ) and said second metallurgical junction (G2) form a double metallurgical junction n-p-n/p-n-p with a double potential barrier composed of said first potential barrier (Vz1) and said second potential barrier (Vz2), where said double metallurgical junction n-p-n/p-n-p comprises a first depletion zone (Z1 ), and a second depletion zone (Z2), in contact with said first depletion zone (Z1 ) along a line of contact (A), disposed within said layer doped p/n (3), said first depletion zone (Z1 ) having a thickness greater than the thickness of the second depletion zone (Z2); said first potential barrier (Vzi) being associated with said first depletion zone (Z 1 ), and said second potential barrier (Vz2) being associated with said second depletion zone (Z2). Said layer doped p/n (3) is dimensioned in such a way that said double potential barrier has a value such as to allow said layer doped p/n (3) being completely deprived of holes/electrons, so that, when a variable electric field is induced by said electromagnetic signal received by said antenna (4), said double metallurgical junction n-p-n/p-n-p is subjected to said variable electric field, and a first potential difference (AV^) and a second potential difference (AVZ2) are generated, through the first depletion zone (Z1 ) and through the second depletion zone (Z2) respectively, where each potential difference (ΔVzi, ΔVz2) is proportional to the thickness of the respective depletion zone (Z1, Z2) and is added algebraically to the respective potential barrier (Vz1, Vz2). The present invention relates also to a charge gathering system comprising said rectifier.