Partially Recessed Anode GaN Schottky Diode
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Solution Overview
Problem
GaN-based Schottky diodes exhibit high forward voltage drop due to the large potential barrier established by the Schottky contact on the AlGaN layer, which also results in reduced reverse blocking voltage when the AlGaN layer is completely removed.
Innovation Solution
A partially recessed anode configuration is used, where one part of the anode is on the surface of the AlGaN layer and another part is recessed within it, directly exposed to the two-dimensional electron gas, reducing the potential barrier and maintaining enhanced reverse blocking voltage by depleting the AlGaN layer under reverse bias.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the AlGaN layer is completely removed to reduce forward voltage drop, then the forward voltage drop decreases, but the reverse blocking voltage is reduced
Solution Approach 1:
The anode is divided into two distinct portions: a first portion that contacts the two-dimensional electron gas layer at the AlGaN/GaN interface, and a second portion that contacts the AlGaN layer surface. This segmentation allows each portion to serve a different function - the first portion reduces forward voltage drop while the second portion maintains reverse blocking voltage.
Solution Approach 2:
Different regions of the anode are given different contact configurations to achieve different local functions. The first portion is positioned to access the low-barrier two-dimensional electron gas, while the second portion maintains contact with the higher-barrier AlGaN layer for reverse blocking, creating local quality variations that resolve the contradiction.
2Ease of operation
If the Schottky contact potential barrier is reduced to improve forward conduction, then the forward voltage drop decreases, but the reverse blocking capability is compromised
Solution Approach 1:
The anode contact is segmented into two portions with different contact locations and functions. The first portion contacts the two-dimensional electron gas to facilitate easy forward conduction with low voltage drop, while the second portion contacts the AlGaN layer to maintain reverse blocking capability, thus resolving the contradiction between ease of operation and reliability.
3Use of energy by moving object
If the anode is fully recessed to reduce forward voltage drop, then the forward voltage drop decreases, but the device complexity increases
Solution Approach 1:
Instead of fully recessing the anode (excessive action), the invention applies partial recession where only the first portion of the anode contacts the two-dimensional electron gas layer while the second portion remains on the AlGaN surface. This partial action achieves the benefit of reduced forward voltage drop without the excessive complexity of full anode recession.
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 partially recessed anode design reduces the forward voltage drop and increases the reverse blocking voltage, improving the overall performance of the Schottky diode by allowing carriers to travel directly through a lower potential barrier while maintaining effective charge blocking.
Implementation Method 1
The junction between the metal and the semiconductor layer forms a rectifying junction with improved diode switching capability... Schottky diodes have lower turn-on voltages and faster switching speeds
Implementation Method 2
The 2-dimensional electron gas is believed to compensate for the strain-induced piezoelectric polarization charges and spontaneous polarization charges arising from the non-ideal nature of the III-nitride crystal structure
Implementation Method 3
The 2-dimensional electron gas is quantum-confined in the band bending region of a hetero-junction where a narrower bandgap III-nitride (e.g., GaN) joins a larger bandgap III-nitride (e.g., AlGaN)
Implementation Method 4
one part of the anode is recessed within it, directly exposed to the two-dimensional electron gas, reducing the potential barrier and maintaining enhanced reverse blocking voltage
Implementation Method 5
maintaining enhanced reverse blocking voltage by depleting the AlGaN layer under reverse bias
Data Source
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AI summary
A semiconductor device such as a Schottky diode is provided which includes a substrate, a first active layer disposed over the substrate and a second active layer disposed on the first active layer. The second active layer has a higher bandgap than the first active layer such that a two-dimensional electron gas layer arises between the first active layer and the second active layer. A first electrode has a first portion disposed in a recess in the second active layer and a second portion disposed on the second active layer such that a Schottky junction is formed therewith. A second electrode is in contact with the first active layer. The second electrode establishes an ohmic junction with the first active layer.