Wafer‐Scale Transferrable GaN Enabled by Hexagonal Boron Nitride for Flexible Light‐Emitting Diode

Abstract

Epitaxy growth and mechanical transfer of high‐quality III‐nitrides using 2D materials, weakly bonded by van der Waals force, becomes an important technology for semiconductor industry. In this work, wafer‐scale transferrable GaN epilayer with low dislocation density is successfully achieved through AlN/h‐BN composite buffer layer and its application in flexible InGaN‐based light‐emitting diodes (LEDs) is demonstrated. Guided by first‐principles calculations, the nucleation and bonding mechanism of GaN and AlN on h‐BN is presented, and it is confirmed that the adsorption energy of Al atoms on O2‐plasma‐treated h‐BN is over 1 eV larger than that of Ga atoms. It is found that the introduced high‐temperature AlN buffer layer induces sufficient tensile strain during rapid coalescence to compensate the compressive strain generated by the heteromismatch, and a strain‐relaxation model for III‐nitrides on h‐BN is proposed. Eventually, the mechanical exfoliation of single‐crystalline GaN film and LED through weak interaction between multilayer h‐BN is realized. The flexible free‐standing thin‐film LED exhibits ≈66% luminescence enhancement with good reliability compared to that before transfer. This work proposes a new approach for the development of flexible semiconductor devices.

2D-Material-Assisted GaN Growth on GaN Template by MOCVD and Its Exfoliation Strategy

“…Therefore, we posit that using h-BN instead of graphene is a more suitable approach for growing exfoliable GaN through 2D-material-assisted growth on a GaN template. This is supported by results demonstrating the successful growth of GaN as a film through h-BN on sapphire, with complete peeling off achieved on a wafer scale …”

“…This is supported by results demonstrating the successful growth of GaN as a film through h-BN on sapphire, with complete peeling off achieved on a wafer scale. 46 Figure 4 shows the Raman spectra and photoluminescence (PL) for the examination of exfoliated GaN. The confirmation of exfoliated GaN was achieved through observation of the Raman E 2 High peak.…”

Shape-deformable Micro-LEDs for advanced displays and healthcare

“…Thickness reduction by substrate removal can impart certain flexibility to Micro-LEDs. Two major strategies have been developed to take off the growth substrate: laser lift-off (LLO) [6,35,36] and epitaxial lift-off (ELO) [37][38][39][40][41][42][43] . LLO exploits the laser energy absorption at the LED layer/substrate interface, which leads to the release of Micro-LEDs from the substrate due to the high-temperature induced material decomposition at the interface [35] [Figure 1A].…”

Flow Modulation Epitaxy of Thick Boron Nitride Epilayers and Wafer-Level Exfoliation

“…Similar to graphene, they are composed of sp 2 -hybridized B–N bonds with a van der Waals (vdW) force between the layers. Due to the wide band gap (∼6 eV), high mechanical strength, and thermal conductivity, sp 2 -BN is often used as the thermal conductivity layer, oxidation resistance layer, insulation layer, and barrier insertion layer of devices. − Moreover, because there are no dangling bonds on the surface and the crystal structure is similar to the c -plane orientation of other III-nitride semiconductors, sp 2 -BN may be used as the ideal buffer layer, which can not only release the lattice mismatch during the epitaxial growth of the heterogeneous substrate but can also enable the exfoliation of the epitaxial layer to fabricate the flexible electronic devices, such as photodetectors, light-emitting diodes, and so on. − Therefore, in order to further develop the aforementioned application fields and fulfill industrial production requirements, it is imperative to grow a thick, uniform, and continuous sp 2 -BN film with a large size.…”