The chemical structure of the ZnO/SiC heterointerface as revealed by electron spectroscopies

Abstract

ZnO layers were deposited on 6H-SiC single crystalline wafers by radio frequency magnetron sputtering. The chemical structure of the ZnO/SiC interface was studied by x-ray photoelectron and x-ray excited Auger electron spectroscopy. A complex chemical structure, involving not only silicon–carbon and zinc–oxygen bonds but also silicon–oxygen and zinc–silicon–oxygen bonds was revealed to form at the ZnO/SiC interface. Based on the comparison with the presumably inert (i.e. chemically abrupt) ZnO/Mo interface, it was concluded that a willemite-like zinc silicate (i.e. Zn2SiO4) interface species develops between ZnO and SiC. The presence of this species at the ZnO/SiC interface will affect the electronic structure of the heterojunction and thus needs to be considered for device optimization.

The isotype ZnO/SiC heterojunction prepared by molecular beam epitaxy – A chemical inert interface with significant band discontinuities

“…Apparently, the interface formed when ZnO is deposited by MBE on SiC is chemically abrupt. This result is – as pointed out above – significantly different from the result of our previous study of the ZnO/SiC interface prepared by RF magnetron sputtering 25 . In the study, the Ap(Zn) changed from 2009.6 to 2010.9 eV with increasing ZnO deposition time (see red data points in the inset of Fig.…”

“…This is significantly different from what we observed in our previous study where the interface was formed by RF-sputtering the ZnO on the SiC substrates. In this case, we found the Si2/(Si1 + Si2) intensity ratio to increase from 2% to 10% upon ZnO deposition 25 , which we explained by the RF-sputter deposition induced formation of a zinc silicate – like species at the ZnO/SiC interface 25 . This suggests that the deposition induced chemical interaction involving Si at the ZnO/SiC interface is more significant if the ZnO is deposited by RF sputtering than by MBE.…”

“…In the study, the Ap(Zn) changed from 2009.6 to 2010.9 eV with increasing ZnO deposition time (see red data points in the inset of Fig. 2 ), indicating a significant chemical interaction at the RF-ZnO/SiC interface that we interpreted as the formation of an interlayer of willemite-like zinc silicate 25 . Thus, in addition to preparation parameters, the choice of the deposition route might offer an alternative means to tailor – by the presence or absence of a Zn 2 SiO 4 -like dielectric interlayer – the chemical (and thus also the electronic) structure of the ZnO/SiC interface.…”

“…However, the chemical and electronic structures of the ZnO/6H–SiC interface prepared by MBE have not been studied in detail. In this paper, we characterize the MBE-ZnO/6H–SiC interface using UV photoelectron (UPS), x-ray photoelectron (XPS) and x-ray excited Auger electron (XAES) spectroscopy and compare our findings to our previous study of the ZnO/6H-SiC interface prepared by radio frequency (RF) magnetron sputtering 25 . We find significant differences in the interface properties that confirm the crucial impact of the ZnO deposition route suggesting an alternative approach for deliberate interface tailoring and device optimization.…”

Stable p‐type ZnO thin films on sapphire and n‐type 4H‐SiC achieved by controlling oxygen pressure using radical‐source laser molecular beam epitaxy

“…Figure shows an I – V characteristic for p‐ZnO/n‐4H‐SiC heterojunction. The turn‐on voltage was larger than 5 V, which may be due to the formation of some very thin oxide such as Zn 2 SiO 4 or some other reasons. Au was used as both p‐ZnO and n‐4H‐SiC electrodes.…”