Detailed light-current-voltage analysis of GaP electroluminescent diodes

Abstract

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.

Gallium Migration Through Contact Metallizations on GaP

“…However, the contacts to GaP cannot be characterized as nonreactive with respect to the oxidation process. Formation of gallium and phosphorus oxides on the gold-based ohmic contacts (2,3) to GaP during galvanic oxidation (1) has been established from electron microprobe analysis (4). It is believed that the presence of oxides on the surfaces of the contacts could be the cause of subsequent bonding difficulties.…”

“…In this work, the origin of the gallium and phosphorus on the surfaces of the contacts to GaP has been investigated by means of secondary ion mass spec-trometry ~ (SIMS). This technique can provide (i) indepth mass spectrometric analyses and (it) ion image displays of sputtered secondary ions generated by a high energy primary ion beam impinging on the specimen (1,(0)(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). With these options, a relative chemical composition profile with depth can be obtained (provided no artifacts are introduced due to relative sputtering yields of the various components of the metallizations) or the area uniformity for a particular species at a given depth can be observed.…”

Sonication Enables Effective Iron Leaching from Green Tuff at Low Temperature

“…It is clear that, when nitrogen-doped, both the p-type and n-type material can contribute significantly to the electroluminescence (EL) depending on the injection ratio re/rh in the device. Further confirmation that this simple theory can explain the quantum efficiency of epitaxial devices can be obtained by studying the diode current against voltage and light output vs voltage characteristics (Wight et a1 1973, Ralston 1973) (figure 4). The current can be separated into diffusion and space-charge recombination components ; and, at least up to current densities -1 A cm-2, the light output is linear with the diffusion component, both having the expected exponential voltage dependence.…”

Metallurgical Structure of Be‐Au and Si‐Au Ohmic Contacts to GaP

“…The samples are polycrystalline bars, 98% dense, sintered from powders prepared by calcination of a homogeneous glassy solid obtained by polymerization of an organic solution in which the cationic constituents have been dissolved in precisely weighed amounts (1). The oxygen activities were obtained by precision-mixed Ar-O2 (high pressure range), CO-CO2 (low pressure range), and by means of an electrochemical oxygen pump and oxygen activity detector based on CaO-doped ZrO2 for the midrange of pressures (2).…”

“…tained with Be-Au and Si-Au metallizations, respectively (1,2). While satisfactory electrically for use in the fabrication of GaP LED's, little information is available regarding the metallurgical structure of these contacts.…”