Defect States in ALD-HfO2 Films on InP Compound Semiconductor as a Function of Film Thickness

Tuesday, 7 October 2014
Expo Center, 1st Floor, Center and Right Foyers (Moon Palace Resort)
Y. Kang, D. Kim, H. Kang, M. H. Cho, S. Cho (Yonsei University), and H. Kim (Sungkyunkwan University)
We investigated the chemical states and nature of the defect states below the conduction band edge of atomic-layer-deposition HfO2 grown on InP substrates as a function of film thickness.  Changes in electronic structure of HfO2 film on InP (001) as a function of film thickness were investigated using high resolution x-ray photoelectron spectroscopy (HR-XPS) and x-ray absorption spectroscopy (XAS). OK1-edge absroption spectra of the HfO2/InP showed the conduction band edge states in HfO2 were increased when the film thickness was increased. DFT calculations and conductance results indicated that these conduction band defect states were caused by the oxygen point vacancy in HfO2 related with Hf3+ states. Moreover, we found the mid-gap states within the InP band gap were caused by out-diffused InP substrate elements into the HfO2 film. By the combination analysis of XAS, XPS, DFT, and conductance, we conclude that (i) the conduction band edge defect states were resulted from the oxygen point vacancy into the HfO2 film, (ii) the mid-gap states within the InP band gap were resulted from the out-diffused P elements into HfO2 film near the HfO2/InP interface.