Influence of AlN buffer layer thickness on material and electrical properties of InAlN/GaN high-electron-mobility transistors

• Published in: Japanese Journal of Applied Physics 2015-07, Vol.54 (7), p.71001
• Main Authors: Huang, Wei-Ching, Liu, Kuan-Shin, Wong, Yuen-Yee, Hsieh, Chi-Feng, Chang, Edward-Yi, Hsu, Heng-Tung
• Format: Article
• Language: English
• Subjects: Aluminum nitride; Buffer layers; Gallium nitrides; High electron mobility transistors; Semiconductor devices; Thickness; Transistors; Two dimensional
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAP.54.071001

The influence of the thickness of a high-temperature AlN (HT-AlN) buffer layer on the properties of an InAlN/GaN high-electron-mobility transistor (HEMT) grown on a sapphire substrate was investigated. As revealed by atomic force microscope analysis, a rougher surface and larger grain size were observed with a thicker buffer layer. The larger grains promoted the two-dimensional (2D) growth mode of the GaN layer at the initial growth stage. This suppressed oxygen incorporation at the GaN/HT-AlN interface and thus improved the resistivity of the GaN layer. Moreover, the lower grain density also resulted in enhanced GaN crystal quality of the GaN layer. As a consequence, the electrical properties of the InAlN/GaN HEMT device, such as output current, transconductance and off-state breakdown voltage, were improved by increasing the HT-AlN buffer layer thickness.