New Applications of III-V Compound Semiconductor Native Oxides for Photonic Devices

The discovery of new materials, the improvement of processing, and the design of new devices are the three engines which boost our modern semiconductor industry. Building upon previous work at the University of Notre Dame on oxygen-enhanced non-selective wet thermal oxidation of low Al content III-V compound semiconductor alloys, which has simplified the fabrication of advanced performance diode laser devices, this work has further expanded the application of III-V native oxides in photonic device fabrication and integration while stimulating additional materials related discoveries.

First, the III-V native oxides grown by our modified wet thermal method are shown capable of improving upon existing wafer bonding techniques. The two flagship compound semiconductors, GaAs and InP, have been successfully bonded to Si substrates using a III-V native oxide as the intermediate layer, with potential applications in erbium doped waveguide amplifier fabrication and in the emerging silicon photonics field. Next, an unexpected gallium oxide film transfer phenomenon observed during wafer bonding of GaAs to Si has generated a promising future research opportunity in the emerging hot area of beta-phase gallium oxide (b-Ga₂O₃) as a wide bandgap semiconductor material, useful for devices such as high-power transistors, solar blind photodetectors, and gas sensing devices. Furthermore, we present detailed preliminary studies on the selective core oxidation of telecommunications wavelength InP-based AlGaInAs laser heterostructure waveguides, including two methods for overcoming the severe, longstanding high temperature process limitations caused by InP dissociation. Using the protection of InGaAs epitaxial regrowth or HfO₂ atomic layer deposition encapsulation, we have successfully selectively oxidized the waveguide core, shrinking the optical confinement region well below the width of the lithographically-defined etched ridge to achieve a single mode waveguide geometry suitable for the design of both active and passive AlGaInAs/InP telecom wavelength devices.