A charge inverter for III-nitride light-emitting diodes

Abstract

In this work, we propose a charge inverter that substantially increases the hole injection efficiency for InGaN/GaN light-emitting diodes (LEDs). The charge inverter consists of a metal/electrode, an insulator, and a semiconductor, making an Electrode-Insulator-Semiconductor (EIS) structure, which is formed by depositing an extremely thin SiO2 insulator layer on the p+-GaN surface of a LED structure before growing the p-electrode. When the LED is forward-biased, a weak inversion layer can be obtained at the interface between the p+-GaN and SiO2 insulator. The weak inversion region can shorten the carrier tunnel distance. Meanwhile, the smaller dielectric constant of the thin SiO2 layer increases the local electric field within the tunnel region, and this is effective in promoting the hole transport from the p-electrode into the p+-GaN layer. Due to the improved hole injection, the external quantum efficiency is increased by 20% at 20 mA for the 350 × 350 μm2 LED chip. Thus, the proposed EIS holds great promise for high efficiency LEDs.

Influence of an Insulator Layer on the Charge Transport in a Metal/Insulator/n‐AlGaN Structure

“…This work also reveals that the bandgap of the insulator has negligible impact on the electron injection for the MIS structure, while the electron injection is very sensitive to the electron affinity and the relative dielectric constant for the insulator, such that the insulator material with a large electron affinity and/or a small relative dielectric constant is preferable, and we suggest Si 3 N 4 and SiO 2 , which are also consistent with the reports in refs. . Moreover, we also find that the electron injection is sensitive to the thickness and the length for the insulator.…”

“…Recently, Nagata et al have proposed to increase the electron injection and reduce contact resistance for the Al‐rich n‐type AlGaN by using thin SiNx intermediate layer. Our group also suggests using SiO 2 thin layer as the intermediate layer on the p‐GaN layer to form the charge inverter for InGaN/GaN blue LEDs, since by doing so, the hole injection is enhanced and the forward voltage is reduced. Although the advantage of the metal‐insulator‐semiconductor (MIS) structure is promising in improving the carrier injection, the detailed physical analysis and systematic discussions lack at this moment.…”

Improving the Current Spreading by Locally Modulating the Doping Type in the n-AlGaN Layer for AlGaN-Based Deep Ultraviolet Light-Emitting Diodes

“…Crosslight APSYS simulator is used to investigate the device physics, and the models that we use are reliable according to our previous publications on blue, UVA, and DUV nitride-based LEDs [22–24]. In our physical models, the energy band offset ratio for the AlGaN/AlGaN heterojunction is set to be 50:50 [25].…”

On the Hole Injection for III-Nitride Based Deep Ultraviolet Light-Emitting Diodes

“…The first obstacle that the injected holes have to overcome arises from the p-GaN/p-ohmic contact interface [ 34 ]. One approach to increase the hole injection at the p-GaN/p-ohmic contact interface is to engineer the p-type metals and improve the intraband tunneling efficiency at the interface.…”