| AVS 61st International Symposium & Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM+2D-TuA |
| Session: | High-k Dielectrics for Advance Semiconductor |
| Presenter: | Xiaoye Qin, University of Texas at Dallas |
| Authors: | X. Qin, University of Texas at Dallas H. Dong, University of Texas at Dallas J.Y. Kim, University of Texas at Dallas R.M. Wallace, University of Texas at Dallas |
| Correspondent: | Click to Email |
AlGaN/GaN high electron mobility transistors (HEMTs) are of significant interest for high power, high frequency and high temperature devices. However, these are known to experience significant surface related effects, such as large leakage currents and frequency dependent current collapse. Oxidation has been found to have a variety of effects on the atomic and electronic structure of nitride surfaces. Therefore, the oxidation layer and the device performance are closely related. Typically, GaN and AlN are found to form a disordered oxide layer related to high density of states when exposure to with O2. Miao et al.1 reported that oxidation of AlN and GaN surface change the density of surface states based on density functional theory (DFT). In their work, a 2 ML crystalline oxide can cause the lowest density of surface states within the band gap. However, experimental evidence of a 2 ML crystalline oxide remains to be established.
In this study, we investigate O2 plasma- exposed AlGaN surfaces at 300 °C and 550 °C by in situ X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED). The results indicate that a 500°C O2 remote plasma exposure is able to generate a thin 2 ML ordered oxide on AlGaN surface and the oxide is stable during subsequent ALD processing, in contrast to arsenide surfaces.2 The capacitance- voltage (C- V) results indicates that the 2 ML crystalline oxide reduces the Dit and shifts the threshold voltage to positive voltages. The I-V and gate leakage current characteristics for crystalline oxide MOSHEMTs will also be presented. This work is supported by the AFOSR Asian Office of Aerospace Research and Development (AOARD) under Grand No. FA2386- 11- 1- 4077.
References
1 M.S. Miao, J.R. Weber, and C.G. Van de Walle, J. Appl. Phys. 107, 123713 (2010).
2 D. M. Zhernokletov, P. Laukkanen, H. Dong, R. V. Galatage, B. Brennan, M. Yakimov, V. Tokranov, J. Kim, S. Oktyabrsky, and R. M. Wallace, Appl. Phys. Lett., 102, 211601 (2013)