IEEE Electron Device Letters | 2021
Improved Channel Electron Mobility Through Electric Field Reduction in GaN Quantum-Well Double-Heterostructures
Abstract
To improve the electron mobility of quantum well (QW) gallium nitride (GaN) high electron mobility transistors (HEMT), we investigated QW and conventional AlGaN/GaN heterostructures grown by metal organic vapor phase epitaxy. Using calculation and experimental results, we revealed that the primary reason for the reduced electron mobility of the QW GaN-HEMT is the increase in intrasubband scattering events because of excessive electron confinement, which is caused by a strong polarization electric field. A strained Al<sub>0.30</sub>Ga<sub>0.70</sub>N/Al<sub>0.86</sub>Ga<sub>0.14</sub>N buffer structure was applied to alleviate the electric field in the GaN channel while maintaining a strong electron confinement. It enables to increase the piezo polarization of Al<sub>0.30</sub>Ga<sub>0.70</sub>N and thus, reduces that of the GaN channel. Consequently, the electron mobility improved to 1420 cm<sup>2</sup>/Vs for the QW GaN-HEMT structure with the Al<sub>0.30</sub>Ga<sub>0.70</sub>N/Al<sub>0.86</sub>Ga<sub>0.14</sub>N buffer from 1100 cm<sup>2</sup>/Vs for the common QW GaN-HEMT structure. To the best of our knowledge, 1420 cm<sup>2</sup>/Vs at a two-dimensional electron gas density of <inline-formula> <tex-math notation= LaTeX >$1.5\\times 10^{{13}}$ </tex-math></inline-formula> cm<sup>−2</sup> is the highest electron mobility in the QW double heterostructure.