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BB4.02 - Growth Comparison Study of High-k Dielectric/GaN Using Atom Probe 
April 23, 2014   8:15am - 8:30am

Al2O3 has emerged as an viable gate dielectric for III-nitride-based electron devices. ALD [1] and MOCVD [2] are the primary growth techniques being used to deposit this dielectric film. A potential advantage of MOCVD is that Al2O3 can be grown in-situ therefore the deposition is free of ambient air contaminants and native oxide growth, and extensive chemical pretreatments which are normally employed before ALD. In this work we have done a growth comparison study of Al2O3/GaN system using atom probe tomography. The 5 nm ALD Al2O3 was grown on a MOCVD GaN/Sapphire template using a H2O first process with H2O pretreatment at a temperature of 300 °C and a pressure of 200 mTorr [1]. The 5 nm MOCVD Al2O3 was grown in situ in the same reactor after GaN growth at a temperature of 900 °C and a pressure of 100 Torr [2]. These samples were then analyzed comparatively in Atom Probe . Mass spectrum analysis of dielectric layer from all the samples show the presence of impurities like C, N etc but no presence of GaxOy was found at the interface. Detailed composition analysis of MOCVD grown oxide shows a stable Al:O ratio throughout the layer and comparatively abrupt interface. On the other hand ALD oxide reveals a diffuse interface. Roughness measurement shows rougher interface for ALD than MOCVD sample. Qualitative estimation of carbon impurities within dielectric was done for both samples and was found to be in the order of 10^19/cm^3. C was suggested as a source of positive fixed near-interface charge and slow near-interface states [3]. Capacitance-voltage (C-V) measurement showed that the slow near-interface states for both ALD and MOCVD sample were on the order of 10^12 cm-2eV-1. However, the MOCVD sample exhibit much less hysteresis and an order of magnitude smaller fast near-interface trap state density (10^11 cm-2eV-1) compared with the ALD sample [1,2,4]. These feedback from atom probe analysis on dielectric/III-V system grown by different techniques is used for growth optimization towards better device fabrication. 1. X. Liu, R. Yeluri, J. Lu, and U.K. Mishra, J. Electron. Mater. 42, 33 (2013).2. X. Liu et al., Appl. Phys. Lett. 103, 053509 (2013).3. M. Choi et al., Appl. Phys. Lett. 102, 142902 (2013).4. X. Liu et al., J. Appl. Phys. 114, 164507 (2013).

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