11 October 2012 High electron mobility AlGaN/AlN/GaN HEMT structure with a nano-scale AlN interlayer
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Epitaxies of AlGaN/AlN/GaN high electron mobility transistor (HEMT) structures with different thickness of nano-scale AlN interlayers have been realized by metalorganic chemical vapor deposition (MOCVD) technology. After epitaxy, high resolution X-ray diffraction (HRXRD), temperature-dependent Hall Effect and atomic force microscopy (AFM) measurements were used to characterize the properties of these samples. First, it was found that the Al composition of AlGaN layer increases from 21.6 to 34.2% with increasing the thickness of AlN interlayer from 0 to 5 nm under the same AlGaN growth conditions. This result may due to the influences of compressive stress and Al incorporation induced by the AlN interlayer. Then, we also found that the room-temperature (RT) electron mobility stays higher than 1500 cm2/Vs in the samples within AlN interlayer thickness range of 1.5 nm, on the other hand, the low-temperature (80K) electron mobility drops dramatically from 8180 to 5720 cm2/Vs in the samples with AlN interlayer thickness increasing from 1 to 1.5 nm. Furthermore, it was found that the two-dimensional electron gas (2DEG) density increases from 1.15×1013 to 1.58×1013 cm-2 beyond the AlN interlayer thickness of 1 nm. It was also found that the temperature independent 2DEG densities are observed in the samples with AlN interlayer thickness of 0.5 and 1 nm. The degenerated characteristics of the samples with AlN thickness thicker than 1.5 nm show the degraded crystalline quality which matched the observation of surface defects and small cracks formations from their AFM images. Finally, the 2DEG mobilities of the proposed structures can be achieved as high as 1705 and 8180 cm2/Vs at RT and 80K, respectively.
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Shih-Chun Huang, Shih-Chun Huang, Wen-Ray Chen, Wen-Ray Chen, Yu-Ting Hsu, Yu-Ting Hsu, Jia-Ching Lin, Jia-Ching Lin, Kuo-Jen Chang, Kuo-Jen Chang, Wen-Jen Lin, Wen-Jen Lin, } "High electron mobility AlGaN/AlN/GaN HEMT structure with a nano-scale AlN interlayer", Proc. SPIE 8467, Nanoepitaxy: Materials and Devices IV, 84670W (11 October 2012); doi: 10.1117/12.929347; https://doi.org/10.1117/12.929347

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