The sapphire substrate pretreatment effects on high-temperature annealed AlN templates in deep ultraviolet light emitting diodes

Abstract

Evolution of crystalline quality of AlN via high-temperature (HT) annealing induced by different sapphire pretreatments is investigated. It is found that after HT annealing at 1700 °C for one hour, an AlN film grown on a nitridation treated sapphire substrate presents a much lower threading dislocation density (TDD) than that grown on an alumination treated one, indicating that the combination of nitridation and HT annealing is a more effective approach to achieve high quality AlN. It is verified that the much greater grain density of the nucleation layer induced by nitridation can produce more columns with much smaller sizes so that they can more easily rotate during the HT annealing to reduce the TDD more effectively. A deep ultraviolet light-emitting diode (285 nm) with an output power over 10 mW has been demonstrated on a HT annealed AlN template with sapphire substrate nitridation pretreatment, showing great potential for applications.