Study of Halogen Doping Aluminum Oxide Deposition on Enhancement-Mode AlGaN/GaN MOS-HEMT

  • 林 志偉

Student thesis: Master's Thesis

Abstract

This thesis proposes the halogen doping of aluminum oxide (Al2O3) stacked on the e-mode AlGaN/GaN high electron mobility transistors (HEMTs) by using ultrasonic spray pyrolysis deposition (USPD) We found that the doping oxide deposit on the enhancement mode AlGaN/GaN HEMTs can achieve more positive threshold voltage shift 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 In addition the decreased oxide layer trap density is confirmed by the hysteresis and interface state density Gate recess fluorine ion implantation and doping oxide are applied to the fabrication of AlGaN/GaN HEMTs We found that threshold voltage of doping oxide device can shift to 1 5V which is more positive 0 3V than only Al2O3 device In addition fluorine ion implantation device has larger drain current and reliability than gate recess device Finally we propose that the Al2O3 oxide layer applied to metal-oxide-semiconductor MOSHEMT by using ultrasonic spray pyrolysis technique is studied the optimal thickness of the oxide layer is 20 nm Gate voltage of device can be operated up to 3V and the breakdown voltage is over 180 V Moreover threshold voltage of device with doping oxide achieves 25 % positive shift Therefore the device which deposited Al2O3 on AlGaN/GaN HEMTs by using ultrasonic spray pyrolysis technique with halogen doping is suitable for modulate threshold voltage and reduce gate leakage
Date of Award2016 Sep 1
Original languageEnglish
SupervisorWei-Chou Hsu (Supervisor)

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