Correlation of in-situ reflectance spectra and resistivity of GaN/Al2O3 interfacial layer in metalorganic chemical vapor deposition

Autor: Rongming Chu, Yugang Zhou, Zhendong Lü, Deliang Wang, Kevin J. Chen, Yundong Qi, Chak Wah Tang, Kei May Lau
Rok vydání: 2005
Předmět:
Zdroj: Journal of Electronic Materials. 34:112-118
ISSN: 1543-186X
0361-5235
DOI: 10.1007/s11664-005-0187-1
Popis: The correlation between the resistivity of an undoped GaN/Al2O3 interfacial layer and in-situ reflectance spectrum in metalorganic chemical vapor deposition and the mechanism of this correlation were investigated. The first minimum reflectance during the initial high-temperature GaN growth was found to be a good indicator of the resistivity of the GaN buffer. The background electron concentration and mobility were both higher in the samples with higher indicative reflectance at that point. The resistivity of the GaN buffer layer was predominantly determined by an ∼0.25-µm-thick layer near the GaN/Al2O3 interface. Atomic force microscope (AFM) and high-resolution x-ray diffraction (HRXRD) results showed that the samples with higher indicative reflectance had smaller sized but higher density nuclei before the high-temperature GaN growth and lower screw threading dislocation (TD) density in the initially grown GaN. The difference in the background electron concentration and mobility of the interfacial layer was related to the relatively higher concentration of the O and Al diffused from Al2O3, which is also dependent on the size and density of the nuclei. These differences were found not to affect the structural and electrical properties or the surface morphology of AlGaN/GaN high electron-mobility transistors (HEMTs, except for the buffer conduction) when the GaN buffer is thick enough (e.g., ∼2.5 µm).
Databáze: OpenAIRE