SBIR Phase I: Development of AlGaN Field Emission Cathodes

这个小企业创新研究（SBIR）第一期项目旨在开发基于iii -氮化物材料的可靠的低压电子发射器。对于场发射应用，期望的宽带隙半导体应具有负电子亲和性，n型掺杂和形成低电阻接触的能力。宽带隙AlxGa1-xN材料（Oxl）由于其低至负电子亲和性，在场发射应用中非常有前途。Alx,Ga1-xN （x0.75）薄膜表现为负电子亲和，而GaN薄膜表现为~3.0 eV的正电子亲和。AIN薄膜本质上是绝缘体。相比之下，氮化镓可以很容易地掺杂n型掺杂剂。我们认为，通过改变AlxGa1-xN组成中x的值，可以同时优化电子亲和值和n型掺杂的场发射应用。在第一阶段，我们将优化AlGaN材料的场发射应用。主要的合成方法是超高真空蒸发与新型氮离子源相结合。特高压蒸发提供了MBE的杂质控制特性，但其生长速率接近于OMCVD。在第二阶段，我们将使用AlGaN渐变层制造和优化各种场发射极器件结构。该技术的潜在商业应用包括真空微电子器件、电子枪、平板显示器和高功率器件。

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.