Novel Devices with Lattice-Matched ScAlN/GaN heterostructures

Novel Devices with Lattice-Matched ScAlN/GaN heterostructures

Our work in the III-Nitride material system is focused on exploiting its unique physical properties to produce novel light sources based on intersubband transitions. Due to the large conduction band offsets available in ScAlN/GaN heterostructures, intersubband transitions can span the technologically important near-IR (~1.5microns) to far-IR (~100microns) spectral range. Demonstration of a quantum cascade laser in this wavelength regime is a primary goal. ScAlN is a promising barrier material for GaN-based quantum structures due to its tunable lattice constant with varying Sc incorporation, enabling lattice-matched ScAlN/GaN heterostructures near ~14% Sc composition. This provides a pathway to reduce strain accumulation and improve structural quality in thick superlattices needed for intersubband devices. Lattice-matched ScAlN/GaN heterostructures also eliminate strain-induced piezoelectric polarization fields however, spontaneous polarization fields remain present and must be considered in device design. Material quality still limits device performance, and ongoing efforts are focused on improving structural quality and interface abruptness to realize ScAlN/GaN superlattice with ultrathin layer thicknesses below 1 nm. Our group studies the structural, morphological and electrical properties of the material we grow by molecular beam epitaxy. We collaborate with the Malis group to study intersubband optical properties.