The design and fabrication of gallium phosphide electroluminescent diodes

The design of an electroluminescent diode involves a tradeoff among optical, thermal, and electrical characteristics. The low absorption coefficient and high refractive index of the gallium phosphide cause the light to spread over a large volume of the semiconductor. Consequently, the optical properties of contacts and surface conditions are critical even when they are well removed from the junction. Low absorption coefficients in the bulk and at the surface, small area wafers and contacts, hemisphere shaped device geometry and anti-reflecting coating contribute to the external quantum efficiency. The internal quantum efficiency is affected by the temperature and the current density of the junction.