Semiconductor Device With Graded Anode For Fast Recovery
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Solution Overview
Problem
Semiconductor devices, such as diodes, face challenges in reducing the recovery time when switching from an ON state to an OFF state due to the slow discharge of carriers, which affects their efficiency in power conversion circuits.
Innovation Solution
The semiconductor device design includes a p type anode region with varying impurity concentrations and an insulating portion between the anode electrode and the n− type semiconductor region, allowing for efficient electron discharge and reducing the likelihood of conduction, thereby shortening the recovery time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carriers are discharged outside when switching from ON state to OFF state, then the semiconductor device can be switched off, but the recovery time becomes long
Solution Approach 1:
The patent applies local quality by creating a p-type region with non-uniform impurity concentration distribution. The impurity concentration is higher near the n-type semiconductor region and lower toward the anode electrode, forming a gradient structure. This localized variation in impurity concentration optimizes the electric field distribution to accelerate carrier discharge specifically in the critical region near the junction, thereby reducing recovery time without compromising overall switching capability.
Solution Approach 2:
The patent changes the impurity concentration parameter within the p-type region to resolve the contradiction. By adjusting the impurity concentration from high near the n-type region to low near the anode, the electric field strength is optimized to facilitate rapid carrier extraction. This parameter modification enables faster recovery time while maintaining reliable switching operation.
2Speed
If impurity concentration is increased to improve carrier discharge, then switching speed improves, but the density of holes increases which may cause unwanted conduction
Solution Approach 1:
The patent uses local quality by implementing a spatially varying impurity concentration profile in the p-type region. The impurity concentration is locally high near the n-type semiconductor region to accelerate electron discharge, and locally low near the anode electrode to maintain proper conduction control. This localized differentiation resolves the contradiction between fast switching and reliable conduction control.
Solution Approach 2:
The p-type region is segmented into zones with different impurity concentrations. The first zone near the n-type region has higher impurity concentration for fast carrier discharge, while the second zone near the anode has lower impurity concentration for conduction control. This segmentation allows simultaneous optimization of both switching speed and conduction reliability.
Data Source
AI summary
A semiconductor device comprising:a first semiconductor region of a first conductivity type;a second semiconductor region of a second conductivity type provided on the first semiconductor region;an insulating portion provided on the first semiconductor region;a third semiconductor region of the second conductivity type provided on the second semiconductor region and having a higher carrier concentration of the second conductivity type than that of the second semiconductor region; anda first electrode provided on the insulating portion and the third semiconductor region, the first electrode having a portion which is aligned with the second semiconductor region in a second direction perpendicular to a first direction being from the first semiconductor region to the second semiconductor region, and the first electrode being in contact with the second semiconductor region and the third semiconductor region.