Abstract
Zinc diffused GaP red electroluminescent diodes with external quantum efficiencies as high as 1.5 per cent at a current density of 1 A/cm 2 have been obtained. The diffusion was from a totally evaporating ZnP 2 source at 900°C into a liquid-phase epitaxial (LPE) layer doped with Te and O. The LPE layer was grown near 1000°C on a liquid-encapsulated Czochralski substrate. Both an open tube vertical ‘dipping’ technique and a closed tube ‘tipping’ system with a slider were used for growth of the LPE layer. The red emission efficiency was increased by a post-diffusion two step anneal. The first is at 750°C for 8 hr and the second is for 16 hr at 525°C. These processing steps have been found to be reproducible. The p- n junctions after annealing are linearly graded with a high resistivity layer 10 −5−10 −6 cm in thickness separating the n and p space charge regions. This high resistivity layer leads to a forward voltage drop in excess of 2.5 V at 10 mA.
Published Version
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