Gallium Nitride (GaN) transistors are quickly revolutionizing RF amplifiers and power converters thanks to its large critical electric field and electron mobility. Until now, all these transistors have been based on electron conduction (i.e. n-type transistors). Although this is common in field effect transistors based on compound semiconductors, the use of n-type-only devices severely limits the design options available to circuit designers. This paper will discuss several new GaN-based transistor structures that enable p-type current conduction with a performance similar to what it is found on n-type GaN transistors. In addition, the careful design of a p-GaN cap layer on top of the AlGaN barrier allows for the fabrication of both enhancement-mode (E-mode) n-channel and p-channel transistors next to each other. We will show how this new structure is compatible with 8” Si substrates and, in combination with the appropriate device fabrication technology, can significantly improve the linearity of RF amplifiers and increase the efficiency of power converters.
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