Atomic layer deposited Y2O3 on GaAs(001)-4x6 - thickness dependence of crystallographic structures and electrical properties and the correlation
C. K. Cheng1*, S. Y. Wu3, K. H. Chen2, C. H. Hsu4, J. Kwo3, M. Hong1
1Grad. Inst. Appl. Phys. and Dept. Phys., Natl. Taiwan Univ., Taipei, Taiwan
2Dept. Phys., Natl. Taiwan Univ., Taipei, Taiwan
3Dept. Phys., Natl. Tsing Hua Univ., Hsinchu, Taiwan
4Research Division, National Synchrotron Radiation Research Center., Hsinchu, Taiwan
* presenting author:鄭兆凱,
Molecular beam epitaxy (MBE) has been used to grow rare-earth oxide films of Gd2O3 and Y2O3 epitaxially on GaAs(001)-4x6, GaAs(111)A, Si(111), and GaN(0001). Interestingly, they have different crystallographic structures with different film thickness on the latter three substrates. On the other hand, atomic layer deposition (ALD) has been widely employed in depositing high  gate dielectrics for the Silicon semiconductor industry due to the precision in film thickness control, the uniformity, and very importantly, the conformal coverage on different substrate geometry. In the work, in-situ ALD has been used to deposit very thin Y2O3 2nm and 5nm thick on GaAs(001)-4x6. The structures have been studied using x-ray diffraction with synchrotron radiation and the interfacial electrical characteristics have been studied using capacitance-voltage (CV) measurement. The in-situ reflective high energy electron diffraction (RHEED) of ALD-Y2O3 on GaAs(001)-4x6 pattern is very intensive, indicating the excellent crystallinity of the films 2 nm and 5 nm thick. It was observed that Y2O3 cubic phase is grown on GaAs with the film (110) plane parallel to GaAs(001) plane. In the surface normal scans, the Y2O3 film thickness was estimated to be nearly 2 nm and 5 nm from the fringes nearby the Y2O3(440) peak. The rocking curve is used to analyze the crystallinity of the films; the full-width-at-half-maximum (FWHM) of the rocking curve for the 2 nm film is 0.033 which is of excellent crystallographic quality, as compared to the FWHM of the commercial GaAs(001) substrate of 0.008. The rocking curve of the 5 nm film is composed of two peaks: FWHM of the smaller peak of better quality is near 0.1, while that of the wider one is 5.6. The CV measurement shows that the dispersion at the accumulation for the 2 nm film is smaller than that for the 5 nm film. The interfacial electrical characteristics are correlated with the crystallographic film quality.

a) Authors contributed equally to this work.
b) To whom correspondence should be addressed. Electronic addresses: (M. Hong), (J. Kwo), and (C. H. Hsu).

Keywords: x-ray diffraction, C-V curve, Y2O3