Optoelectronic Properties and Structural Characterization of GaN Thick Films on Different Substrates through Pulsed Laser Deposition

Abstract

Approximately 4-µm-thick GaN epitaxial films were directly grown onto a GaN/sapphire template, sapphire, Si(111), and Si(100) substrates by high-temperature pulsed laser deposition (PLD). The influence of the substrate type on the crystalline quality, surface morphology, microstructure, and stress states was investigated by X-ray diffraction (XRD), photoluminescence (PL), atomic force microscopy (AFM), transmission electron microscopy (TEM), and Raman spectroscopy. Raman scattering spectral analysis showed a compressive film stress of −0.468 GPa for the GaN/sapphire template, whereas the GaN films on sapphire, Si(111), and Si(100) exhibited a tensile stress of 0.21, 0.177, and 0.081 GPa, respectively. Comparative analysis indicated the growth of very close to stress-free GaN on the Si(100) substrate due to the highly directional energetic precursor migration on the substrate's surface and the release of stress in the nucleation of GaN films during growth by the high-temperature (1000 • C) operation of PLD. Moreover, TEM images revealed that no significant GaN meltback (Ga-Si) etching process was found in the GaN/Si sample surface. These results indicate that PLD has great potential for developing stress-free GaN templates on different substrates and using them for further application in optoelectronic devices.

Structural Characteristics and Photoluminescence Properties of Sputter-Deposition ZnGa2O4 Thin Films on Sapphire and Si(100) Substrates

“…The FWHM values of ZnGa 2 O 4 (111) grown on the sapphire and Si(100) substrates were measured as 0.29 • and 0.49 • , respectively. The lower FWHM on sapphire than on silicon is consistent with larger crystallites formed by aggregation of small grains or grain boundary movement during the film deposition process [19]. The grain sizes of ZnGa 2 O 4 grown on the two substrates were calculated by the Debye-Scherer equation [20]:…”

Effect of Substrates on the Dynamic Properties of Inkjet-Printed Ag Thin Films

“…The electrical performance of thin film transistors was optimized by adjusting the thickness of the film [18]. The electrical resistivity and physical deformations of the film after sintering were also related to the substrate [19,20].…”

Effect of GaN substrate thickness on the optical field of InGaN lasers diodes

“…Another problem in fabrication of nitrides based LDs is the lack of native GaN substrates. Presently InGaN based LDs are grown onto sapphire or SiC substrates [8]. This results in high threading dislocation densities in the structure because of thermal and lattice mismatch [9,10].…”

“…To fabricate efficient waveguides with not optical leakage, very thick claddings layers are usually gown in arsenidebased lasers. Unfortunately, in case of nitride material system, there is a significant lattice mismatch between AlN and GaN [8], which strongly limits the thickness attainable in the AlGaN cladding layers. AlGaN layers thicker than the critical thickness tend to crack and the stress introduced in the Al x Ga 1−x N cladding layers results in poor quality material [7,17].…”