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Monitoring the growth of III-nitride materials by plasma assisted molecular beam epitaxy employing diffuse scattering of RHEED
S. Sen, S. Paul, C. Singha, A. Saha, A. Das, P. Guha Roy, P. Pramanik,
Published in AVS Science and Technology Society
Volume: 38
Issue: 1
AlGaN alloys find important applications in UV emitters and detectors, as well as in high-power high-frequency electronics. While reflection high energy electron diffraction (RHEED) is a standard technique for in situ monitoring of the growth of AlGaN alloys by plasma assisted molecular beam epitaxy, this paper investigates a new mode of its application. During the growth of AlGaN alloys, the ratio of the group III (Al + Ga) to group V (active nitrogen) adatoms critically controls the materials property of AlGaN films and is optimal within a very narrow window of operation. Moreover, this ratio is dependent in a complex fashion on various growth parameters, including substrate temperature, and is difficult to determine quantitatively in real time. This paper provides a method to estimate that important parameter. This can be carried out through the capture of the RHEED image from the fluorescent screen using an inexpensive video camera setup and a simple analysis procedure. While most RHEED analyses focus on the diffraction pattern, e.g., the line spacing, this work quantifies diffused scattering of the electron beam from a metallic layer that forms on the top of the growth surface during deposition under excess group III conditions, which is typically employed during growth. Two alternate methods for data analysis have been explored and compared. The results indicate that this process can qualitatively trace the variation of the thickness of the thin metallic layer, and hence the group III to group V flux ratio, for different substrate temperatures. This technique being simple, fast, and cost-effective can be incorporated into standard MBE systems for real-time in situ characterization of AlGaN alloys. © 2019 Author(s).
About the journal
JournalJournal of Vacuum Science and Technology B: Nanotechnology and Microelectronics
PublisherAVS Science and Technology Society