Thermal Oxidation of AlInN for III-Nitride Electronic and Optoelectronic Devices

The oxidation of semiconductors is a fundamental building block of many modern electronic devices. The prime example is the oxidation of silicon into silicon dioxide, which is used as a gate dielectric, waveguides, masking layer, and a device isolation layer. The ability to form an analogous stable and insulating oxide in III-nitride semiconductors would enable a new generation of III-nitride-based electronic and optoelectronic devices. Here we present data on the conversion of thick (>100 nm) AlInN epitaxial layers into oxides with H2O vapor in an N2 carrier gas (wet oxidation) at elevated temperatures (900 °C). The AlxIn1–xN layers are grown on and latticed-matched (x = 0.82) to GaN layers. The oxide can be formed over its entirety or selectively by patterning the surface. The conversion to an oxide is confirmed and characterized by atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, spectroscopic ellipsometry, and electrical measurements. The oxide is smooth and crystalline, has a low index of refraction of ∼1.8 in the visible, and exhibits very high resistivity of >1014 Ω·cm.