Green emitting Zn-diffused LPE GaP diodes

The growth of liquid phase epitaxial (LPE) layers of n-type GaP on GaP substrates was investigated using a multi-wafer growth system constructed of fused quartz which had provisions for gas phase saturation and doping of the gallium melt. The effect of growth temperature, substrate orientation, doping level, and repeated use of the same melt on the properties of zinc diffused electroluminescent diodes fabricated from these epitaxial layers were investigated. After an initial increase, the carrier concentration remained relatively constant (1.7 × 10¹⁷/cc) throughout a series of eighteen runs from the same melt. Using conventional commercial techniques, zinc diffused diodes with efficiencies of 0.05% at 30A/cm² and a brightness of 1200 fL at 10A/cm² were produced. These diodes had a limited area n and p-type contact and had an epoxy dome. Layers grown on the 〈 111 〉P orientation had the best surface quality whereas those grown on the 〈 100 〉 plane incorporated less background impurities. The use of relatively low growth starting temperatures (∼ 920°C) was found to minimize the background impurity of the layers and the substrate surface deterioration due to the reaction with ammonia. This work was, in part, sponsored by the Air Force Materials Laboratory under the direction of Mrs. E. H. Tarrants, contract number F33615-71-C-1621