Current Spreading in Back-Contacted GaInP/GaAs Light-Emitting Diodes

Abstract

The recently proposed diffusion-driven charge transport (DDCT) method can allow a paradigm shift in the design of optoelectronic devices, by changing both the current injection principle and the device structure. The DDCT injection technique is based on the bipolar electron and hole diffusion currents that are used to electrically inject charge carriers into an active region (AR) located outside the p-n junction. In this article, we study an interdigitated back-contacted DDCT-light-emitting diode (LED) based on a GaInP/GaAs double heterojunction (DHJ) structure consisting of lateral heterojunctions (LHJs) located above a uniform AR. The structure uses single-sided electrical injection and is suitable for large-area applications and thin-film devices with near-surface ARs. Our analysis, based on charge transport simulations, suggests that the structure permits more efficient current spreading and lower surface recombination than conventional structures, leading to a very high internal quantum efficiency (IQE) and injection efficiency exceeding 99%. Particularly, we investigate the implications of using the new structure for improving the efficiency of LEDs, bringing them closer to the threshold of electroluminescent cooling (ELC). The results predict an above-unity internal power conversion efficiency for the DDCT-LEDs, substantially exceeding the efficiency of conventional reference devices, highlighting the new possibilities that DDCT devices offer especially for high-power ELC at room temperature.

Directly addressable GaN-based nano-LED arrays: fabrication and electro-optical characterization

“…6, the current density in the current spreading layer is plotted as a function of the distance from the edge of the metal contact. According to the theory of current spreading 24 , the current spreading length, defined as the distance between the metal edge position and the point, where the current density reaches 1/e of the original current density J 0 , depends on the current density and decreases as the current density increases. According to Eq.…”

Interdigitated back‐contact double‐heterojunction GaInP/GaAs solar cells

“…Therefore, a clear functional difference between these designs is that even if the AR is removed from the DDCT structure, the p-n junction still forms a working device. As such, in terms of current transport, the EBAC solar cell design is very similar to the conventional two-side contacted structures, and it also leaves a significant part of the AR exposed to surface recombination which can substantially reduce the device efficiency, as recently discussed in Myllynen et al 19 within the LED context. The DDCT approach does not suffer from such limitation, since both surface and interface recombination can be readily minimized.…”

“…The first steps towards IBC technology for compound semiconductor devices were only taken very recently through modelling efforts of emitter-less back-surface alternating contact (EBAC) III-As solar cells 17,18 and diffusion-driven charge transport (DDCT) light-emitting diodes (LEDs). 19,20 On the surface, these devices are similar in the sense that both structures have contacts only on the back and that charge carriers migrate to the active region (AR) through the same surface. In more fundamental terms, however, they have one crucial difference.…”

Silicon-Integrated III–V Light Emitters and Absorbers Using Bipolar Diffusion

“…Figure 1 illustrates a potential solution to the problem of electrical injection of NWs on silicon. In the proposed approach, the NWs are electrically injected without top contacts by taking advantage of diffusion-driven charge transport (DDCT) [34][35][36][37][38][39] and lateral doping of silicon. DDCT has been previously reported in GaAs [36] and GaN [37][38][39] light emitters, theoretically as well as experimentally.…”

“…In the proposed approach, the NWs are electrically injected without top contacts by taking advantage of diffusion-driven charge transport (DDCT) [34][35][36][37][38][39] and lateral doping of silicon. DDCT has been previously reported in GaAs [36] and GaN [37][38][39] light emitters, theoretically as well as experimentally. The simulations of this paper are carried out to show that combined with the remarkable diffusion lengths in silicon and existing lateral-doping techniques, it offers a path toward fully silicon-integrated electrically injected free-standing NW light emitters and absorbers.…”