Study of AlN/GaN HEMTs

The large polarization difference between AlN and GaN provides extremely high electron densities at the heterointerface covered by only 3-4 nm AlN barrier, which makes AlN/GaN heterojunction the ultimate nitride structure for high-frequency applications. This work includes the systematic study of the MBE growth of AlN/GaN HEMTs, theoretical study of 2DEG scattering mechanisms, and device issues of in-situ buffer leakage removal with polarization engineering and decreasing contact resistance with band diagram engineering. This book shows the approach to achieve the record high 2DEG density (5e13/cm2) and the record-low sheet resistance (128 ohm/sq) in high-quality AlN/GaN HEMTs. As a theoretical study, electron scattering mechanisms are reviewed in this book. A novel scattering mechanism, remote surface roughness scattering, is proposed. Large buffer leakage and ohmic contact resistance are two factors that heavily degrade high-speed device performance. Polarization engineering was applied in the buffer leakage study, which increased the ON/OFF ratio by 4 orders. Regrown Si-doped GaN and graded InGaN/InN contacts have been demonstrated with a comprehensive X-ray diffraction study.

Autorentext

Yu Cao received B.S. degree in Phys from Nanjing University in 2002 and M.S. degree in Electrical Engineering in 2003 from Natl Univ. of Singapore. He has been a graduate student in the Dept. of Elec. Eng., Univ of Notre Dame since 2005.