Effects of nitrogen impurity on zno crystal growth on Si substrates
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.28
Effects of nitrogen impurity on zno crystal growth on Si substrates Soichiro Muraoka1, Lyu Jiahao1, Daisuke Yamashita1, Kunihiro Kamataki1, Kazunori Koga1, Masaharu Shiratani1, and Naho Itagaki1 1 Graduate School of Information Science and Electrical Engineering, Kyushu University, Motooka 744, Fukuoka, 819-0395, Japan
ABSTRACT
Effects of nitrogen impurity on ZnO crystal growth on Si substrates have been investigated. The quantitative analysis on the surface morphology deriving height-height correlation function indicates that adsorbed nitrogen atoms suppress the secondary nucleation and enhance adatom migration. The resultant films have smooth surface as well as large grain size up to 24 nm even for small thickness of 10 nm. ZnO films fabricated by using such films as buffer layers possess high crystal quality, where the full width at half maximum of (002) rocking curve is 0.68°, one-fourth of that for films fabricated without nitrogen.
Introduction ZnO is a multi-functional material with a distinctive property set and a wide range of existing and emerging applications such as varistors, transparent conducting electrodes, surface-acoustic-wave (SAW) devices, thin film transistors, and gas sensors [1-5]. ZnO has also been recognized as a candidate materials for high performance ultraviolet light-emitting diodes (LEDs) and laser diodes (LD) due to the large exciton binding energy of 60 meV, much larger than that of a commercial LED material, GaN (25 meV). However, fabrication of efficient ZnO-based p-n homojunction has been challenging because ZnO is intrinsically a n-type semiconductor [6]. Although significant progress has been made in the achievement of p-type conductivity in ZnO, the growth of reproducible high quality p-type ZnO still awaits further development. In this context, some research has been directed toward fabrication of n-ZnO/p-Si heterojunctions that have not only significant advantages in terms of cost and wafer size but also a great impact on Si integrated circuit technology.
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Due to the large lattice mismatch of 15% between ZnO and Si(111), however, ZnO films prepared on Si substrates by a conventional method possess a large number of crystal defects that surely deteriorate the device performance. One of the most promising means to improve the crystal quality is to prepare buffer layers prior to the film growth. So far, low-temperature (LT) buffer layers have been utilized for the film growth on lattice mismatched substrates. The idea of LT buffer layers was first reported for the mean of GaN growth on sapphire substrates, where the lattice mismatch is 16%. The LT buffer layers provide adequate density of crystal nucleation site, and thus lead to relaxation of the latti
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