Green and Red Electroluminescences from Diffused Gallium Phosphide p-n Junctions

Abstract

Electroluminescent p-n junctions were prepared by zinc diffusion into n-GaP crystals doped with tellurium, but not intentionally doped with oxygen. Annealing at 800°C after diffusion at 1000°C improved red emission efficiency of diodes about one hundred times and green emission efficiency seven times. For annealed diodes, red efficiency monotonically decreased with diffusion time, whereas green efficiency showed a maximum between 2 and 4 hours, about four times the value for one hour diffusion. Green efficiencies obtained under optimum conditions are of the order of 10^-5 at 10 A/cm² and increases with current up to 1×10^-4 for 100 A/cm². Annealing-time and diffusion-time dependences of green and red emissions were well interpreted on the basis of junction profiles revealed from capacitance data. At 77°K, junctions showed characteristics of p-i-n structure; abrupt changes in emission spectra were observed around currents inducing negative resistance, according to a change in injection mechanism.