Atomic Layer Deposition of Complex Oxides for Novel Devices

随着加拿大和世界其他地区迅速转向可再生能源，支持可再生能源的电子产品正成为人们关注的焦点。 可再生能源，如光电子，产生直流（DC）电力，必须转换成交流（AC）电力，以供电网和许多家用电器使用。 DC到AC功率转换由电路中使用的逆变器完成，该逆变器可以根据电路设计产生不同类型的交流功率（方波、修正正弦波、脉冲正弦波、脉宽调制波或正弦波）。 在DC电压小于期望的AC电压的情况下使用其他电路，并且升压电路用于在DC电压被逆变之前将DC电压增加到所需的电平。 这些逆变器和升压电路的核心是大功率器件，主要基于硅。 许多用于光伏发电的硅逆变器电路的效率只有80%，这意味着20%的太阳能被浪费了！众所周知，III-V功率器件可用于构建高效率（>95%效率）逆变器，但这些器件非常昂贵。我们已经开发出一种低温工艺来制造氮化镓（GaN）和（氧化锌）ZnO金属氧化物半导体器件。GaN用于功率器件（逆变器），而ZnO用于制造显示器中使用的薄膜晶体管。我们对这些材料的栅极氧化物（氧化铪，氧化铝，氧化锆）的初步研究已经给出了非常有前途的结果。 然而，功率器件对栅氧化层的要求很高，一些二元栅氧化层的性能不能满足所有的要求。 例如，我们具有界面缺陷低但体缺陷太高的栅极氧化物，并且我们具有体缺陷低但界面缺陷高的栅极氧化物。 为了解决这个问题，Cadien博士建议研究更复杂的氧化物和氧化物结构，以找到满足功率和薄膜器件应用所需所有规格的组合。

As Canada and the rest of the world rapidly moves towards renewable energy, the electronics that support renewable energy is coming into focus. Renewable energy, such as photovoltaics, generates direct current (DC) power that must be converted into alternating current (AC) power to be used by the grid and many household appliances. DC to AC power conversion is accomplished by inverters used in circuits that can generate different types of alternating power (square wave, modified sine wave, pulsed sine wave, pulse width modulated wave or sine wave) depending on circuit design. Other circuits are used in cases where the DC voltage is less than the desired AC voltage and a boost circuit is used to increase the DC voltage to the required level before it is inverted. At heart of these inverters and boost circuits are high power devices, mostly based on silicon. Many silicon inverter circuits used in photovoltaics are only 80% efficient, which means that 20% percent of the solar power is wasted! It is well known that III-V power devices can be used to build high efficiency (>95% efficient) inverters, but these devices are very expensive. We have developed a low-temperature process to fabricate Gallium Nitride (GaN) and (Zinc Oxide) ZnO metal-oxide-semiconductor devices. GaN is used in power devices (inverters) while ZnO is used to fabricate thin film transistors that are used in displays. Our initial research into gate oxides (hafnium oxide, aluminum oxide, zirconium oxide) for these materials has given very promising results. However, the gate oxide requirement for power device is very demanding and some of the binary gate oxide properties can not meet all fo the requirements. For example, we have gate oxides with low interfacial defects but bulk defects that are too high, and we have gate oxides with low bulk defects but high interfacial defects. In order to solve this problem, Dr. Cadien is proposing to look at more complex oxides and oxide structures in order to find a combination that meets all of the required specifications for power and thin film device applications.