Diffusion-Driven Charge Transport in Light Emitting Devices

Abstract

Almost all modern inorganic light-emitting diode (LED) designs are based on double heterojunctions (DHJs) whose structure and current injection principle have remained essentially unchanged for decades. Although highly efficient devices based on the DHJ design have been developed and commercialized for energy-efficient general lighting, the conventional DHJ design requires burying the active region (AR) inside a pn-junction. This has hindered the development of emitters utilizing nanostructured ARs located close to device surfaces such as nanowires or surface quantum wells. Modern DHJ III-N LEDs also exhibit resistive losses that arise from the DHJ device geometry. The recently introduced diffusion-driven charge transport (DDCT) emitter design offers a novel way to transport charge carriers to unconventionally placed ARs. In a DDCT device, the AR is located apart from the pn-junction and the charge carriers are injected into the AR by bipolar diffusion. This device design allows the integration of surface ARs to semiconductor LEDs and offers a promising method to reduce resistive losses in high power devices. In this work, we present a review of the recent progress in gallium nitride (GaN) based DDCT devices, and an outlook of potential DDCT has for opto- and microelectronics.

Defect Passivation in Lead‐Halide Perovskite Nanocrystals and Thin Films: Toward Efficient LEDs and Solar Cells

“…Under an applied electrical bias, the ions (halide ions or A‐site cations) can migrate via defects, thereby causing material degradation which is irreversibly detrimental to device stability [72a] . Methods such as making diffusion‐driven charge‐transport LEDs [75] and effective diffusion engineering of the charge injection layers [76] would be future directions to suppress ion migration in planar LEDs. In this Review, we will only focus on improving PeLED performance by mitigating the effects of defects to improve device efficiency and stability (Figure 8).…”

Back‐Contacted Carrier Injection for Scalable GaN Light Emitters

“…[ 22 ] Especially the injection efficiency challenge has encouraged us to study the DDCT concept instead in laterally doped and back‐contacted devices in Refs. [24,25].…”

“…All previous approaches to create back‐contacted GaN devices have required the use of methods that are not conventionally used in the fabrication of GaN LEDs, such as selective area growth (SAG) and ion implantation, introducing additional uncertainties in the fabrication. [ 24,26,27 ] Nevertheless, according to our previous simulation results, successful implementation of such back‐contacted structures could ultimately lead to improved carrier spreading and thereby even enable exceeding the efficiency of comparable DHJ structures. [ 25 ] In addition to improved carrier spreading, the major potential advantages of back‐contacted structures would be the possibility to extract light through the bottom side as in a flip‐chip structure, and the removal of all free MQW surfaces close to the contact edges prone to surface recombination.…”

A Facile and Low-Cost Method to Produce Ultrapure 99.99999% Gallium

“…Gallium (Ga), one of the important raw materials used in contemporary semiconductor industry, was discovered in 1875 [1], and has been significantly utilized in the industry since the 1940s. Ga and its compounds are extensively used in advanced electronic devices [2,3,4], integrated circuits [5,6,7], and thin-film solar cells [8,9] because these compounds can provide the benefits of low energy consumption and high computation speeds.…”