Electrical effects and thermal stability of plasma damage in aluminum gallium nitride alloys. Ahad Ali Syed

ISBN: 9781109416091

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107 pages


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Electrical effects and thermal stability of plasma damage in aluminum gallium nitride alloys.  by  Ahad Ali Syed

Electrical effects and thermal stability of plasma damage in aluminum gallium nitride alloys. by Ahad Ali Syed
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The focus of this thesis is the electrical effects and thermal stability of plasma damage in AlGaN alloys. The effects of surface treatment using Ar and Cl2/BCl3 inductively coupled plasmas on the rectifying characteristics of Pt/Au contacts to AlxGaMoreThe focus of this thesis is the electrical effects and thermal stability of plasma damage in AlGaN alloys.

The effects of surface treatment using Ar and Cl2/BCl3 inductively coupled plasmas on the rectifying characteristics of Pt/Au contacts to AlxGa 1-xN (x=0--0.5) were investigated. Plasma treatment increased the conductivity of GaN and Al 0.1Ga0.9N surfaces, making the rectifying contacts into Ohmic contacts. For higher Al-content AlGaN, the Schottky diodes turned leaky after Cl2/BCl3 plasma treatment, where damage creation and etching occur simultaneously, whereas the diodes become more rectifying upon Ar plasma exposure, in which plasma damage accumulates.

A time-dependent study of Ar plasma treatment supports the hypothesis that the energy level of plasma damage in high-Al content AlGaN may be damage density dependent, and damage accumulation during Ar plasma exposure results in a high-resistivity region compensated by deep-level defect states.-Further, the thermal stability of as-grown and plasma-treated Al xGa1-xN (x=0--0.5) has been studied. High temperature annealing up to 800°C in N2 ambient after plasma treatment produced significant recovery of the IV characteristics of Schottky diodes while at temperatures higher than 800°C, the characteristics were degraded due to preferential surface loss of nitrogen and localized surface dissociation.

A more complete removal of plasma damage in AlGaN requires annealing at temperatures >800°C with a careful surface protection. Schottky contacts formed on as-grown AlGaN samples subjected to high temperature annealing in an Ar ambient show improvement in the electrical characteristics up to 800°C. After annealing at higher temperatures, the GaN Schottky diodes became leakier, whereas the AlGaN diodes were more rectifying, confirming that N vacancies are shallow donors in GaN, but act as deep-level states in high-Al AlGaN. These new findings emphasize the need to reduce plasma damage introduced during etching processes required to fabricate AlGaN-based electronic and optoelectronic devices.



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