Fundamental understanding and development of novel high dielectric constant ALD gate oxides on gallium nitride substrates for MOSFET power conversion applications

氮化镓（GaN）是高温、大功率、高频金属氧化物半导体场效应晶体管（MOSFET）的最佳候选材料之一。用GaN制成的功率器件有可能提供比硅高500倍以上的开关速度。实现该技术的关键组件是开发具有低缺陷和优先迁移率特性的鲁棒氧化物，其可以产生增强型晶体管而不是耗尽型晶体管。然而，由于电介质/GaN界面处的大量界面态，通过栅极氧化物的栅极漏电流和费米能级钉扎限制了它们在此类应用中的使用。目前，没有单一材料能够满足GaN的所有氧化物要求。此外，氧化物必须满足各种要求，例如大的带隙以增加击穿电压。 拟议的研究计划的长期目标是开发GaN高功率MOSFET器件的功率转换应用，如混合动力汽车和太阳能电池阵列的新型栅极氧化物。 这项长期研究将与阿尔伯塔大学电气和计算机工程系的器件物理学家和GaN技术专家道格拉斯·巴拉奇教授合作进行。 短期目标是发展对GaN上栅极氧化物的原子层沉积（ALD）生长的基本理解，并开发新型GaN栅极氧化物和结构。主要的焦点将是研究纳米层压材料形式的高k金属氧化物的组合，以将所有所需的特性，如大带隙材料和大介电常数引入GaN MOS结构的栅极材料。氧化物将通过ALD沉积，以受益于该技术的许多优点，包括对厚度的出色控制、低温沉积、无针孔和高度共形薄膜。这些氧化物的化学，微观结构和化学计量的原子层沉积膜的电性能的影响将被探讨。

Gallium Nitride (GaN) is one of the best candidates for high-temperature, high-power, and high-frequency metal-oxide-semiconductor field-effect transistors (MOSFETs). Power devices made with GaN have the potential to offer a switching speed with a figure of merit more than 500 times greater than that achievable in silicon. The critical component to enable this technology is the development of a robust oxide with low defects and preferential mobility properties that can produce an enhancement mode transistor rather than a depletion mode transistor. However, gate leakage current through the gate oxide and Fermi-level pinning due to large number of interface states at dielectric/GaN interface limit their usage in such applications. Currently, no single material has the ability to cover all the oxide requirements for GaN. Moreover, the oxides must fulfill various requirements such as a large band gap to increase the breakdown voltage. The long term objective of the proposed research program is to develop novel gate oxides for GaN high power MOSFET devices for power conversion applications such as hybrid cars and solar cell arrays. The long term research will take place in collaboration with Professor Douglas Barlage, a device physicist and expert in GaN technology, in Electrical and Computer Engineering at the University of Alberta. The shorter term objectives are to develop a fundamental understanding of the atomic layer deposition (ALD) growth of gate oxides on GaN, and to develop novel GaN gate oxides and structures. The main focus will be to investigate the combinations of high-k metal oxides in the form of nanolaminates to introduce all the required properties, such as large bandgap materials and large dielectric constant, to the gate material of GaN MOS structure. The oxides will be deposited by ALD to benefit from the many advantages of this technique, including excellent control on thickness, deposition at low temperatures, pinhole-free, and highly conformal thin films. The effect of chemistry, microstructure, and stoichiometry of these oxides on the electrical properties of atomic layer deposited films will be explored.