Power semiconductors
Which is the channel through which current flows in a GaN HEMT?
- AA p-type inversion layer formed under the gate
- BA thick, heavily doped n-type layer
- CA two-dimensional electron gas (2DEG) formed by polarization at the AlGaN/GaN interface
Show answer and explanation
Answer: C. A two-dimensional electron gas (2DEG) formed by polarization at the AlGaN/GaN interface
In a GaN HEMT, spontaneous and piezoelectric polarization create a high-density two-dimensional electron gas (2DEG) at the AlGaN/GaN interface. Electrons travel in a region with little impurity scattering, so mobility is high, enabling high-frequency, high-efficiency switching. Because the 2DEG exists even at 0 V gate voltage, the basic structure is normally on.