Interface Trap Density Reduction for Al2O3/GaN (0001) Interfaces by Oxidizing Surface Preparation prior to Atomic Layer Deposition

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• 作者：Dmitry M. Zhernokletov ; Muhammad A. Negara ; Rathnait D. Long ; Shaul Aloni ; Dennis Nordlund ; Paul C. McIntyre
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：June 17, 2015
• 年：2015
• 卷：7
• 期：23
• 页码：12774-12780
• 全文大小：423K
• ISSN：1944-8252

文摘

We correlate interfacial defect state densities with the chemical composition of the Al₂O₃/GaN interface in metal-oxide-semiconductor (MOS) structures using synchrotron photoelectron emission spectroscopy (PES), cathodoluminescence and high-temperature capacitance鈥搗oltage measurements. The influence of the wet chemical pretreatments involving (1) HCl+HF etching or (2) NH₄OH_(aq) exposure prior to atomic layer deposition (ALD) of Al₂O₃ were investigated on n-type GaN (0001) substrates. Prior to ALD, PES analysis of the NH₄OH_(aq) treated surface shows a greater Ga₂O₃ component compared to either HCl+HF treated or as-received surfaces. The lowest surface concentration of oxygen species is detected on the acid etched surface, whereas the NH₄OH treated sample reveals the lowest carbon surface concentration. Both surface pretreatments improve electrical characteristics of MOS capacitors compared to untreated samples by reducing the Al₂O₃/GaN interface state density. The lowest interfacial trap density at energies in the upper band gap is detected for samples pretreated with NH₄OH. These results are consistent with cathodoluminescence data indicating that the NH₄OH treated samples show the strongest band edge emission compared to as-received and acid etched samples. PES results indicate that the combination of reduced carbon contamination while maintaining a Ga₂O₃ interfacial layer by NH₄OH_(aq) exposure prior to ALD results in fewer interface traps after Al₂O₃ deposition on the GaN substrate.