Design and analysis of high electron mobility transistor inspired: III-V electro-optic modulator topologies

Abstract

III-V heterostructure based high electron mobility transistors (HEMTs) offer superior performance as compared to CMOS silicon transistors owing to the high mobility in the 2D electron gas (2DEG) channel at the heterostructure interface. Gallium nitride (GaN) based HEMTs are also suitable for high power and high temperature applications. GaN has a rich offering of material properties spanning domains of non-linear optics, piezoelectric micro-electro-mechanical systems, and monolithic microwave integrated circuits. In this paper, we propose HEMT inspired III-V electro-optic modulator topologies and study the light interaction with 2DEG in such structures. We analyze the electroabsorption and electrorefraction on account of the 2DEG interaction with light and present a design framework to selectively leverage the desired mechanism of modulation. Our analysis suggests that modulation index of electrorefractive modulation in a HEMT-like structure is comparable to silicon photonic modulators. By leveraging the higher electron mobility in these material platforms, the device concepts proposed here could potentially be used to design electro-optic modulators with extremely high modulation rates.