Speaker
Description
Scandium diboride (ScB2) is a refractory semi-metallic ultrahard ceramic crystal that is lattice matched to ultra-wide bandgap (UWBG) AlGaN. The lattice match of ScB2/Al0.55Ga0.45N would reduce the strain and crystal defects of epitaxial layers enabling thicker pseudomorphic drift layers >5um for high voltage vertical power devices >5kV on these semi-metallic substrates, while eliminating the substrate series resistance parasitic.
We demonstrate the growth of ScB2 crystals by the laser-diode floating zone (LDFZ) method. Poly-crystalline ScB2 rods were used as our feed and seed rods, and Sc as flux, with a starting resistivity of ~400μΩcm. Our growth rate is ~2mm/hr giving a typical total growth of >20mm long. X-Ray Diffraction (XRD) data shows clear signatures of (001) ScB2. Laue measurements on cut/polished samples show six-fold symmetry over mm length scales, with room temperature bulk resistivity ~20μΩ-cm, ~20x lower than the starting feed material. Heat-capacity measurements were performed at temperatures 2K<T<300 K and were analyzed to quantify the contributions of phonons and electrons. The Debye temperature (θD~710K) and the electronic coefficient (γ ~ 3.8 mj.mol^(-1).K^(-2)) of heat capacity Determined. These samples had thermal conductivity ~100 W/m-K at the level of Si and GaN, showing the potential for substrates from an electrothermal co-design perspective.
| Academic or Professional Status | Graduate Student |
|---|
