Fabrication and characterisation of non-polar M-plane AlN crystals and LEDs

Aluminium nitride crystals and devices grown along the polar c-axis direction are affected by the strong spontaneous and piezoelectric polarisation fields. It is necessary to grow non-polar plane aluminium nitride crystals in order to solve the problem. The M-plane surface-oriented aluminium nitride single crystals were grown by physical vapour transport on a resistance heating furnace, which was designed by ourselves and included two heaters on sublimation region and crystalline region, respectively. The M-plane aluminium nitride light-emitting diode was further fabricated and characterised. The current–voltage characteristic showed a Schottky diode behaviour. A white light emission from the biased diode can be clearly seen by naked eyes in a dark place at room temperature. The ultra-wide electroluminescent spectrum covered from deep UV (200 nm) to infrared (1100 nm) and centred at 496 nm (2·5 eV). At last, the emission mechanism was discussed.