GaN HEMT Impurity Region Suppresses Substrate Leak Current
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Solution Overview
Problem
Conventional GaN-based HEMTs face challenges in suppressing leak current due to electron-hole pair generation in semiconductor substrates with small band gaps, such as silicon or silicon carbide, especially under high-voltage and high-temperature conditions, limiting their maximum operating voltage.
Innovation Solution
Incorporating an impurity-containing region in the semiconductor substrate with a level deeper than the conduction band edge by 0.25 eV and shallower than the valence band edge, which acts as a recombination center to quickly recombine electron-hole pairs, thereby reducing carrier lifetime and leak current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional semiconductor substrate with small band gap (silicon or silicon carbide) is used, then it is easy to obtain large diameter and high quality at low cost, but electron-hole pairs are generated under high-voltage conditions causing leak current that limits maximum operating voltage
Solution Approach 1:
An impurity-containing region is introduced as an intermediary layer between the semiconductor substrate and the GaN-based HEMT structure. This region acts as a mediator that captures and recombines carriers, preventing them from reaching the drain electrode and causing leak current, thus enabling high-voltage operation while maintaining the use of conventional substrates
Solution Approach 2:
The harmful effect of carrier generation in the substrate is extracted and isolated by creating a dedicated impurity-containing region. This region is specifically designed to capture carriers generated in the substrate, separating the substrate's mechanical and electrical support functions from the active device regions, thereby preventing substrate-induced leak current
2Power
If high-voltage operation is attempted in conventional GaN-based HEMT, then high output power is achieved, but leak current increases due to electron-hole pair generation and separation in the substrate
Solution Approach 1:
The impurity-containing region converts the harmful effect of carrier generation into a beneficial recombination mechanism. By intentionally introducing impurities that create recombination centers, carriers that would otherwise cause leak current are rapidly recombined, transforming the substrate's inherent carrier generation problem into a controlled recombination zone that protects the high-voltage operation
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 introduction of the impurity-containing region effectively suppresses leak current by ensuring electron-hole pair recombination before separation, enhancing the maximum operating voltage of GaN-based HEMTs.
Implementation Method 1
the impurity forms a level lower than a lower edge of a conduction band of silicon by 0.25 eV or more, the impurity forms the level higher than an upper edge of a valence band of silicon
Data Source
AI summary
A compound semiconductor device includes: a semiconductor substrate; a channel layer over the semiconductor substrate; a carrier supply layer over the channel layer; and a gate electrode, a source electrode and a drain electrode above the carrier supply layer. The semiconductor substrate includes an impurity-containing region containing an impurity, the impurity forms a level lower than a lower edge of a conduction band of silicon by 0.25 eV or more, the impurity forms the level higher than an upper edge of a valence band of silicon.