Remote Epitaxy of β-Ga2O3 on SiC via Pulsed Laser Deposition

Abstract

Remote epitaxy of β-Ga2O3 on graphene-covered SiC substrates offers a potential solution to the poor thermal conductivity that limits this ultra-wide bandgap material. To achieve this, the growth of β-Ga2O3 by pulsed laser deposition (PLD) was optimised first on bare 4H-SiC substrates and subsequently transferred to graphene-covered SiC. The growth parameters were selected to maximise both the crystalline quality and growth rate of the deposited films while preserving
the structural integrity of the graphene layer during growth.

A minimum rocking curve FWHM value of 2.38 ◦ ± 0.07 ◦ was achieved for growth on graphene-covered SiC, compared with 1.01 ◦ ± 0.02 ◦for growth on bare SiC under optimised conditions. Furthermore, films grown on monolayer graphene exhibited narrower FWHM values than those grown on multilayer graphene under otherwise identical conditions. The lower crystalline quality observed for growth on graphene indicated that the graphene layer played a central role in determining the epitaxial quality of the deposited β-Ga2O3 films. These results highlight the challenges associated with achieving remote epitaxial growth of β-Ga2O3 with high crystal quality, and suggest that growth mechanisms in addition to ideal remote epitaxy may contribute to film formation. The preservation of graphene was exhibited for the two-step growth with the best relative crystallinity, mentioned above. The Raman results further suggested that maintaining the structural integrity of graphene during growth was important for achieving improved epitaxial film quality.

Popular Abstract

Modern electronic devices used in electric vehicles, power grids and renewable energy systems require materials that can handle high voltages and temperatures. β-Ga2O3 has been highlighted as a promising material for future high-power electronics due to its ultra-wide bandgap and high breakdown voltage. However, β-Ga2O3 has one major disadvantage: it does not conduct heat efficiently. This can lead to over-heating which can reduce device performance and reliability.

One promising solution to this problem is a process called remote epitaxy. In this method, a very thin graphene layer is placed between the substrate and the growing crystalline film. This graphene layer acts as a release layer, allowing the grown β-Ga2O3 film to be peeled off like a sticker, producing a free-standing single-crystalline film. This film can then be transferred to another material with a better thermal conductivity. This could improve heat dissipation in future electronic devices

In this work, β-Ga2O3 films were grown using a technique called pulsed laser deposition (PLD). In PLD, a pulsed laser strikes a ceramic target, creating a plasma plume of ablated material that is then deposited onto a heated substrate surface. PLD is a very versatile method, and many growth parameters can be changed. In this work, the substrate temperature, chamber pressure and atmosphere and their effects on growth rate, relative crystalline quality and surface morphology were investigated and optimised.

A major challenge of remote epitaxy is that graphene can degrade at high temperatures and in oxygen-rich environments, which are normally required to grow high quality β-Ga2O3 films. To overcome this issue, a two-step growth method was implemented. First, a buffer layer was grown at low temperature and high argon pressure to protect the graphene layer. Afterwards, the temperature was increased, and oxygen was introduced to improve the crystalline quality and growth rate of the ‘main’ film layer.

This process first required optimisation of β-Ga2O3 growth via PLD in both argon and oxygen atmospheres on bare SiC substrates. After this, two-step growths were carried out on bare SiC substrates before being applied to graphene-covered substrates. Several characterisation techniques were then used to evaluate and compare the deposited films. These methods measured growth rate, crystalline quality, surface structure, graphene integrity and the presence of defect states.

Crystalline quality was assessed using the FWHM values of rocking curve scans performed using X-ray diffraction (XRD). A broader FWHM value indicated greater crystal misalignment and an increased defect density within the films. The best crystalline quality achieved for films grown on graphene-covered SiC showed a rocking curve FWHM value of 2.38° ± 0.07°, compared with 1.01° ± 0.02° for films grown directly on bare SiC under optimised conditions in this work. Films grown on monolayer graphene showed an improved crystalline quality to that of films grown on multilayer graphene under identical growth conditions. Both these results show that the graphene layer strongly influenced the quality of the single-crystalline β-Ga2O3 films. Surprisingly, films grown on graphene-covered substrates consistently showed poorer crystalline quality than those grown on bare SiC. This suggested that the graphene layer disrupted the epitaxial growth process and that conventional remote epitaxy was not the dominant growth mechanism occurring in this work.

Therefore, future work should focus on investigation of the graphene layer before growth, including thickness, coverage and defect density. A long-term goal would be the development of highly controlled graphene layers. The removal process of the deposited film should also be attempted. If successful, characterisation of the film before and after removal from the graphene should be done to assess how the removal process affects the quality of the β-Ga2O3 film.

• author: Carey, Grace
• supervisor: Vanya Darakchieva; Andri Dhora
• organization: Solid State Physics; Department of Physics
• alternative title: Distans-epitaxi av beta-Galliumoxid på SiC via pulserad-laser deposition
• course: PHYM03 20261
• year: 2026
• type: H2 - Master's Degree (Two Years)
• subject: Physics and Astronomy; Technology and Engineering
• keywords: remote epitaxy, epitaxy, semiconductor, ultra-wide bandgap, gallium oxide, silicon carbide, Ga2O3, SiC, pulsed laser deposition, PLD, growth, characterisation, crystal quality, growth rate, high-power devices, single crystalline, thin films, deposition
• language: English
• id: 9243207
• date added to LUP: 2026-06-28 10:50:49
• date last changed: 2026-06-28 10:50:49