Influence of stress in GaN crystals grown by HVPE on MOCVD-GaN/6H-SiC substrate

Abstract

GaN crystals without cracks were successfully grown on a MOCVD-GaN/6H-SiC (MGS) substrate with a low V/III ratio of 20 at initial growth. With a high V/III ratio of 80 at initial growth, opaque GaN polycrystals were obtained. The structural analysis and optical characterization reveal that stress has a great influence on the growth of the epitaxial films. An atomic level model is used to explain these phenomena during crystal growth. It is found that atomic mobility is retarded by compressive stress and enhanced by tensile stress.

Three-dimensional Aerographite-GaN hybrid networks: Single step fabrication of porous and mechanically flexible materials for multifunctional applications

“…Multistep processes, for example synthesis followed integration, have been applied to fabricated nanostructures based devices but this approach is very time consuming and equally expensive. In order to overcome these issues, either direct growth of semiconductors on the desired substrates/chips 27 28 or the fabrication of large 3D interconnected networks made from these nano- and microstructures building blocks must be realized by appropriate techniques 29 30 31 . Such three dimensionally interconnected network structures exhibit all the features inherent to nanoscopic dimensions and in addition they are very easy to handle and hence they are even more flexible for various advanced applications.…”

Direct Observation of the Biaxial Stress Effect on Efficiency Droop in GaN-based Light-emitting Diode under Electrical Injection

“…An increase in the E 2 phonon frequency with respect to unstrained GaN indicates compressive stress, whereas a decrease implies tensile stress. For stress-free GaN films, the E 2 Raman phonon frequency is located at 567.1 cm −1 20 21 , which corresponds to wavelengths of 501.9, 548.6, and 656.6 nm for the laser lines of 488, 532, and 633 nm, respectively, as shown in Fig. 1(a) .…”

“…2(a,b) , the E 2 mode decreases as the current increases and reaches 565.5 cm −1 with a downshift of 4.4 cm −1 when the driving current on the GaN-based LEDs increases to 700 mA. Given that the E 2 phonon frequency is affected by biaxial stress, the E 2 phonon frequency shift Δ ω can be used to characterize the biaxial stress σ a of the GaN layer according to the following relationship 20 :…”

“…Based on the above relation, the biaxial stress under different current injections is determined through the E 2 phonon frequency shift Δ ω with respect to unstrained GaN. Given that the E 2 phonon frequency in the stress-free GaN is known to be located at 567.1 ± 0.1 cm −1 20 , the calculated compressive stress of 0.65 GPa in Fig. 2(c) is considered reasonable in GaN-based LEDs without current injection.…”

Study of nanostructures and interfaces of technological materials by means of electron microscopy techniques

“…1-5 shows the lattice constants and bandgap energies for wurtzite and zinc blende group III-nitride materials, also including the commonly used substrates for the growth of epilayers. The materials properties for GaN, AlN and InN are presented in Table 1-1 [7]- [10]. The lattice mismatch between III-nitride materials and the most commonly used substrates results in a high dislocation density, affecting the mechanical and optoelectronic properties in the epilayers as well as the surface morphology of epilayers.…”