Nitride Semiconductor Diode Recess Structure for Low On-State Voltage
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Solution Overview
Problem
Nitride-based semiconductor devices face challenges in achieving low on-state voltage while maintaining low reverse-bias leak current due to the piezoelectric charge and lattice distortion issues in the barrier layer, making it difficult to reduce the Schottky barrier height without increasing the reverse-bias leak current.
Innovation Solution
A nitride-based semiconductor device structure is developed with a recess structure in the barrier layer, allowing for a thinner barrier layer thickness near the anode electrode, which reduces the carrier density and minimizes reverse-bias leak current, and uses an ohmic contact material for the electrodes to achieve low on-state voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the Schottky barrier height is decreased to lower the on-state voltage, then the on-state voltage is reduced, but the reverse-bias leak current increases
Solution Approach 1:
The barrier layer is designed with different aluminum composition ratios in different regions: a first region with lower Al composition (0.2-0.4) under the anode electrode to reduce Schottky barrier height and on-state voltage, and a second region with higher Al composition (0.4-0.6) in peripheral areas to suppress reverse-bias leak current. This spatial variation in material composition resolves the contradiction between low on-state voltage and low reverse-bias leak current.
Solution Approach 2:
The barrier layer is segmented into multiple regions with different Al composition ratios. The first region (central area) has Al composition 0.2-0.4 for low barrier height, while the second region (peripheral area) has Al composition 0.4-0.6 for high breakdown voltage. This segmentation allows each region to optimize for its specific function, resolving the trade-off between on-state voltage and reverse-bias leak current.
2Use of energy by moving object
If a metal with low work function is used for the anode electrode to decrease the Schottky barrier height, then the on-state voltage is lowered, but the reverse-bias leak current increases
Solution Approach 1:
Instead of changing the electrode material (which would affect both on-state voltage and reverse-bias leak current), the invention changes the barrier layer's Al composition ratio parameter. The first region has Al composition 0.2-0.4 to reduce Schottky barrier height for low on-state voltage, while the second region has Al composition 0.4-0.6 to maintain high breakdown voltage and suppress reverse-bias leak current.
3Use of energy by moving object
If the barrier layer thickness is reduced to lower the Schottky barrier height, then the on-state voltage is decreased, but the reverse-bias leak current increases
Solution Approach 1:
The barrier layer thickness is optimized locally: the first region under the anode electrode has smaller thickness (10-50 nm) to reduce Schottky barrier height and on-state voltage, while the second peripheral region has larger thickness (50-100 nm) to suppress reverse-bias leak current and enhance breakdown voltage. This local thickness variation resolves the contradiction.
Solution Approach 2:
The barrier layer is segmented into a first region with thickness 10-50 nm for low on-state voltage and a second region with thickness 50-100 nm for low reverse-bias leak current. This thickness segmentation allows simultaneous optimization of both parameters.
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 device achieves a low on-state voltage and reduced reverse-bias leak current by depleting the two-dimensional electron system under the recess structure, enhancing the breakdown voltage and operational efficiency.
Implementation Method 1
a distortion occurs in the barrier layer. In the nitride-based semiconductor, piezoelectric charge is produced in the barrier layer due to the piezo effect caused by the distortion in the barrier layer. The piezoelectric charge produced at that time causes a two-dimensional electron gas to be formed at the interface between the carrier traveling layer and the barrier layer.
Data Source
AI summary
A nitride-based semiconductor device includes a diode provided on a semiconductor substrate. The diode contains a first nitride-based semiconductor layer made of non-doped AlXGa1-XN (0≦X<1); a second nitride-based semiconductor layer made of non-doped or n-type AlYGa1-YN (0<Y≦1, X<Y) having a lattice constant smaller than that of the first nitride-based semiconductor layer; a first electrode formed on the second nitride-based semiconductor layer; a second electrode formed on the second nitride-based semiconductor layer; and an insulating film that covers the second nitride-based semiconductor layer below a peripheral portion of the first electrode. In the diode, a recess structure portion is formed at a position near the peripheral portion of the first electrode on the second nitride-based semiconductor layer, and the first electrode covers the second nitride-based semiconductor layer and at least a part of the insulating film.