Cubic Boron Nitride PN Junction Diode Made at High Pressure as a High Temperature Diode and an Ultraviolet LED

The temperature difference method was applied to grow a large crystal of cubic boron nitride (cBN) under ?>55 kbar and ?> 1700°C using LiCaBN2 as a solvent. cBN crystals of ?>3 mm in size were obtained. A pnjunction diode of cBN was then fabricated by growing a silicon-doped n-type crystal epitaxially on a beryllium-doped p-type seed crystal. Formation of the pn junction was clearly confirmed by rectification characteristics and by the existence of a space charge layer of the junction as observed by electron beam induced current (EBIC) measurement. The rectification characteristics were observed from room temperature to 650° C. Injection luminescence was observed at the cBN pn junction. Microscopic observation showed that the whitish blue light was emitted only in the forward-bias condition. Spectroscopic studies revealed that the spectra had a peak in the ultraviolet and the shortest observed wavelength was ?>215 nm.