Vacuum High Temperature Oven with Graphitic Isolation

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The high temperature annealing (HTA) of highly defective (~ 1011 cm-2) sputter-deposited AlN layers on sapphire substrates recently turned out to be a promising method for defect reduction. AlN proved itself as one of the few compound semicondutors that can be annealed at high temperatures without dissociation, similiar to silicon. During the defect annealing process, the as-sputtered layers are heated to temperatures up to 1750 °C. So far, mostly nitrogen atmospheres are used during high temperature annealing. Meanwhile, there are clear experimental indications, backed by phase diagram considerations, that an annealing step under reactive gas atmosphere e.g. CO or NH3 may lead to stabilization of the AlN and thus makes annealing at even higher temperatures possible. The HTA process at higher temperatures targets for an further increase of crystal quality.Therefore, we propose the acquisition of a high temperature vacuum furnace with a graphite heater and a graphite thermal insulation. The planned work is not only interesting from a scientific point of view, but would result in an enabling technology for more efficient UV-LEDs as well as nitride-based power electronics, where leakage currents react sensitive to the density of screw dislocations. Overall, the proposed furnace should offer reactive gas atmospheres (H2, CO, NH3) and inert/reactive gas mixtures at temperatures up to at least 1750 °C.