SBIR Phase I: Development of AlGaN Field Emission Cathodes

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9860931 This Small Business Innovation Research (SBIR) Phase I project aims to develop reliable, low-voltage electron emitters based on III-nitride materials. For field-emission applications, the desired wide band-gap semiconductor should negative electron affinity, n-type doping and ability to form low-resistance contacts. The wide-band-gap AlxGa1-xN materials (Oxl) are very promising for field-emission applications because of their low to negative electron affinity. Alx,Ga1-xN (x0.75) films exhibit a negative electron affinity while GaN exhibits a positive electron affinity of ~3.0 eV. AIN films are essentially insulators. In contrast, GaN can be doped easily with n-type dopants. We believe that by changing the value of x in the AlxGa1-xN composition, the value of electron affinity and n-type doping can be simultaneously optimized for field-emission applications. In Phase-I, we will optimize the AlGaN materials for field-emission applications. The primary synthesis approach is ultra high vacuum evaporation in combination with a novel nitrogen ion source. UHV evaporation offers the impurity control characteristic of MBE, but at growth rates approaching those for OMCVD. In Phase-II, we will fabricate and optimize various field emitter device structures using AlGaN graded layers. Potential commercial applications of this technology include vacuum microelectronic devices, electron guns, flat-panel displays and high power devices.