Strain Analysis of GaN HEMTs on (111) Silicon with Two Transitional AlxGa1−xN Layers

• Published in: Materials 2018-10, Vol.11 (10), p.1968
• Main Authors: Cai, Yuefei, Zhu, Chenqi, Jiu, Ling, Gong, Yipin, Yu, Xiang, Bai, Jie, Esendag, Volkan, Wang, Tao
• Format: Article
• Language: English
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma11101968

We have designed and then grown a simple structure for high electron mobility transistors (HEMTs) on silicon, where as usual two transitional layers of AlxGa1−xN (x = 0.35, x = 0.17) have been used in order to engineer the induced strain as a result of the large lattice mismatch and large thermal expansion coefficient difference between GaN and silicon. Detailed x-ray reciprocal space mapping (RSM) measurements have been taken in order to study the strain, along with cross-section scanning electron microscope (SEM) images and x-ray diffraction (XRD) curve measurements. It has been found that it is critical to achieve a crack-free GaN HEMT epi-wafer with high crystal quality by obtaining a high quality AlN buffer, and then tuning the proper thickness and aluminium composition of the two transitional AlxGa1−xN layers. Finally, HEMTs with high performance that are fabricated on the epi-wafer have been demonstrated to confirm the success of our strain engineering and above analysis.