A p-n junction diode of cubic boron nitride was made by growing an n-type crystal epitaxially on a p-type seed crystal at a pressure of 55 kilobars and a temperature of about 1700 degrees C. A temperature-difference solvent method was used for the crystal growth, and beryllium and silicon were doped as acceptors and donors, respectively. Formation of the p-n junction was clearly confirmed at 1 bar by rectification characteristics and by existence of a space charge layer of the junction as observed by electron beam induced current measurement. This diode operated at 530 degrees C.

A graphite relative of composition BC2N has been subjected to high-pressure (7.7 GPa) and high-temperature (2000-2400 °C) conditions to explore the possibility for the formation of a cubic phase via direct transformation. Several cubic phases with a diamond-like structure were confirmed in the products above 2150 °C by the powder X-ray diffraction patterns. The deconvolution of the broad and partly split diffraction lines suggested that the products obtained at 2150-2300 °C consisted of cBN, "diamond" (containing minor amount of B and N), and a cubic B-C-N substance. At 2400 °C, however, the cubic products tended to segregate into two major phases assigned as cBN and "diamond". This tendency was strongly supported by the microstructural and elemental observation of the products using a highresolution scanning electron microscope and Auger electron spectroscopy. The present study concludes that not a cubic B-C-N compound but a mixture of cBN and diamond exists as the thermodynamically stable phases in the ternary system under the conditions employed.

Injection luminescence in the ultraviolet is observed from a cubic boron nitride pn junction diode made at high pressure. Microscopic observation and spectroscopic studies show that the light emission occurs near the junction region only in the forward-bias condition. The spectra extend from ∼215 nm to the red, having a few peaks mainly in the ultraviolet.

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