Study of Al2O3 Deposition on AlGaN/GaN HEMT by Using Ultrasonic Spray Pyrolysis Technique

  • 吳 宇勝

Student thesis: Master's Thesis

Abstract

This research proposes the investigation of aluminum oxide (Al2O3) and stacked Si3N4/Al2O3 on the AlGaN/GaN high electron mobility transistors (HEMTs) by using ultrasonic spray pyrolysis deposition (USPD) We found that the stacked Si3N4/Al2O3 on the AlGaN/GaN HEMTs achieved better reliability and lower leakage current In order to analyze the oxide layer composition we utilized the atomic force microscopy (AFM) transmission electron microscopy (TEM) electron spectroscopy for chemical analysis (ESCA) and Hall measurement in the research We observe that the surface roughness is quite uniform by AFM Then we confirm that the thickness of oxide layer is 20 nm through TEM Besides in ESCA analysis the results show the oxide layer is exactly Al2O3 Moreover Hall measurement is compared with passivated device the sheet concentration is increased and the electron mobility slightly reduced In addition the decreased oxide layer trap density is confirmed by the hysteresis and interface state density Si3N4 Al2O3 and stacked passivation are applied to the fabrication of AlGaN/GaN HEMTs We found that stacked passivation device can suppress gate leakage to be 3 6×10-4 mA/mm which is better than 2 9×10-2 mA/mm of Si3N4-passivated device Furthermore anti-corrosion and reliability of the stacked passivation device is better than Al2O3-passivated device Finally we propose that the Al2O3 oxide layer applied to metal-oxide-semiconductor (MOS) HEMTs by using ultrasonic spray pyrolysis technique is studied the optimal thickness of the oxide layer is 20 nm The gate voltage of device can be operated up to 4 V and the breakdown voltage is -182 V Moreover the power-add efficiency (P A E ) achieves 42 % Therefore the device which passivated Al2O3 on the AlGaN/GaN HEMTs by using ultrasonic spray pyrolysis technique is suitable for high power and high frequency applications
Date of Award2014 Aug 5
Original languageEnglish
SupervisorWei-Chou Hsu (Supervisor)

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