Detailed light-current-voltage analysis of GaP electroluminescent diodes

The light-current-voltage (LIV) characteristics of both red- and green-emitting GaP p-n junctions have been analyzed in detail at room temperature. Device current has been quantitively and accurately decomposed into components corresponding to the Sah-Noyce-Shockley space-charge recombination and to diffusion current. Data analysis is performed rapidly using an automatic iterative procedure developed for this purpose. In the course of calculation, diode resistance in series with the junction is measured and corrected for, thus considerably extending the upper limit of bias current which may be usefully studied. This study has also determined the current dependence of injection efficiency, electroluminescent quantum efficiency, and the effective luminescent recombination efficiency of the bulk semiconductor region adjacent to the junction. Although this method is applicable to broad classes of junction devices, its use involves certain limitations and ambiguities, which are explicitly discussed. This analysis has been applied to the LIV characteristics of representative examples of both red- and green-light-emitting GaP p-n junctions, grown by double liquid-phase epitaxy. For both these cases, it is demonstrated that the simple current models employed (SNS space charge and diffusion) are in excellent agreement with the observed I-V characteristics over more than nine decades of device current. It seems apparent that these techniques will prove relevant to studies of the physics of light-emitting diodes.