Tungsten CVD Precursors

Halide precursors (HVPE)

Tungsten Hexachloride WCl6

  • Melting point 281.5°C
  • Boiling point 348°C
  • Condensed phase density 3.52g/cm3 (at 25°C)
  • Molar mass 396.57 g/mol
WCl6 saturated vapor pressure
Saturated vapor pressure of Tungsten Hexachloride (WCl6)

Tungsten Hexafluoride WF6

  • Melting point 2.5°C
  • Boiling point 17.3°C
  • Condensed phase density 4.56 g/cm3 (solid T<-8.5°C), 3.99 g/cm3 (solid at 0°C), 3.4 g/cm3 (liquid at 20°C)
  • Molar mass 297.84 g/mol

 

Stevenson, F. D., Wicks, C. E., & Block, F. E. (1963). Vapor pressure of tungsten (VI) chloride and hafnium (IV) iodide by a metal diaphragm technique (No. BM-RI-6367). Bureau of Mines, Albany, OR (USA). Albany Metallurgy Research Center.

Siegel, S., & Northrop, D. A. (1966). X-ray diffraction studies of some transition metal hexafluorides. Inorganic Chemistry, 5(12), 2187-2188

Alyea, E. D., Gallagher, L. B., Mullens, J. H., & Teem, J. M. (1957). A WF6 bubble chamber. Il Nuovo Cimento (1955-1965), 6(6), 1480-1488.

 

Thermal management of high power HB LED

The efficiency of transformation of electricity into the light is a key point for HB LEDs. Efficiency of the typical LEDs achieves 40% to 50%. That means that more than 50% of the electrical power transforms into heat. The reason is a numerous of non-radiative recombination channels in the LEDs, because of high density of dislocations and point defects, and light extraction losses.

The strategic fight for LED high efficiency is the fight for high quality of the material and, in particular, for low dislocation density. Therefore, GaN or AlN substrates should be used to get high efficient HB LEDs or low threshold LDs.

However, the shortest way to get HB LEDs today is to increase electrical power applied to the LEDs and to improve LEDs thermal management at the same time.

Continue reading Thermal management of high power HB LED