June 14, 2012
Hydrogen Radicals ‘Heals’ Plasma-Damaged Semiconductor
Gallium nitride (GaN) is a highly promising material for a wide range of optical and high-power electronic devices, which can be fabricated by dry etching with plasmas. However, the plasma-induced defects and surface residues that remain after such processes tend to degrade the optical and electrical properties of the devices. A team of Japanese researchers has developed and tested a new way to "heal" such defects.
The team exposed plasma-damaged GaN to hydrogen (H) radicals at room temperature. After testing various doses of H radicals, the researchers evaluated the optical properties of the GaN. The intensity of light emitted when electrons near the edge of the valence shell in GaN absorbed and then re-emitted photons drastically decreased after chlorine plasma-beam etching. After treatment with the higher-level doses of H radicals, however, the photoluminescence was restored to almost the level of un-etched GaN.The H radicals likely terminated the dangling bonds of Ga on the GaN surface, as well as desorbed the surface residues, which both led to the recovered optical performance. A key characteristic of the new healing process, described in a paper accepted to the American Institute of Physics' journal AIP Advances, is that it is performed in situ immediately after the etching process. This is important because unwanted surface oxidation can easily occur on plasma-damaged GaN that is exposed to air.
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