Structural and Photoelectronic Properties of κ-Ga2O3 Thin Films Grown on Polycrystalline Diamond Substrates

Abstract

Orthorhombic κ-Ga2O3 thin films were grown for the first time on polycrystalline diamond free-standing substrates by metal-organic vapor phase epitaxy at a temperature of 650 °C. Structural, morphological, electrical, and photoelectronic properties of the obtained heterostructures were evaluated by optical microscopy, X-ray diffraction, current-voltage measurements, and spectral photoconductivity, respectively. Results show that a very slow cooling, performed at low pressure (100 mbar) under a controlled He flow soon after the growth process, is mandatory to improve the quality of the κ-Ga2O3 epitaxial thin film, ensuring a good adhesion to the diamond substrate, an optimal morphology, and a lower density of electrically active defects. This paves the way for the future development of novel hybrid architectures for UV and ionizing radiation detection, exploiting the unique features of gallium oxide and diamond as wide-bandgap semiconductors.

A Review of β-Ga2O3 Power Diodes

“…Experiments have demonstrated that integrating β-Ga 2 O 3 heterostructures onto highthermal-conductivity substrates can effectively enhance device heat dissipation. One of the most effective solutions is to utilize diamond substrates to grow Ga 2 O 3 thin films, due to the excellent thermal conductivity of diamond, which can effectively dissipate heat [254][255][256][257][258]. However, due to lattice mismatch, the quality of β-Ga 2 O 3 films grown by heteroepitaxy is often poor, limiting device performance [259][260][261].…”

Thermodynamics of Ga2O3 Heteroepitaxy and Material Growth Via Metal Organic Chemical Vapor Deposition

“…As can be seen in Figure 2 , the post growth cooling rate may influence the formation of macroscopic defects and the overall layer quality; it was not studied systematically for the samples under study. 35,44 ■ RESULTS AND DISCUSSION Figure 3 shows the XRD 2θ−ω scans of the grown samples. All the samples display consistent peaks at 18.9°, 38.4°, and 59.2°, which can be attributed to the (−201), (−402), and (−603) crystallographic planes, respectively, of the beta polymorph of Ga 2 O 3 .…”

“…A post growth cooling rate of 70 °C/min was used for all the samples studied here. As outlined by Girolami et al, the post growth cooling rate may influence the formation of macroscopic defects and the overall layer quality; it was not studied systematically for the samples under study. , …”

“… 7 Recent successes in this domain include the high-quality epitaxial growth of Ga 2 O 3 on diamond achieved by Nandi et al 8 and Karim et al 9 Besides, Girolami et al recently demonstrated growth of κ-Ga 2 O 3 on polycrystalline diamond substrates. 44 Furthermore, several reports have outlined the successful heteroepitaxy of Ga 2 O 3 on SiC substrates, opening new avenues for enhanced device performance and thermal management.…”

“…However, challenges exist in direct bonding, as Cheng et al pointed out the limitation of weak van der Waals bonding between the substrate and the Ga 2 O 3 layer; this hinders the full utilization of the thermal conductivity in diamond and SiC substrates 7. Recent successes in this domain include the high-quality epitaxial growth of Ga 2 O 3 on diamond achieved by Nandi et al8 and Karim et al9 Besides, Girolami et al recently demonstrated growth of κ-Ga 2 O 3 on polycrystalline diamond substrates 44. Furthermore, several reports have outlined the successful heteroepitaxy of Ga 2 O 3 on SiC substrates, opening new avenues for enhanced device performance and thermal management.Recent research, such as Hrubisak et al's work on liquid injection metal−organic chemical vapor deposition (MOCVD) growth of monoclinic β-Ga 2 O 3 films on 4H-SiC,…”