Abstract
The phase transformation of GaN bulk from the Wurtzite phase (WZ) to the hexagonal phase (HX) is studied by molecular dynamics simulation. The mechanical response and atomic structural evolution of transition are analyzed in detail. In addition, the loading rate effect on the phase transition is determined, that is, the phase transition ratio declines with a decrease of the strain rate. The WZ GaN bulk completely transforms into the HX phase in the case of compression at an ultrahigh strain rate. However, at a relatively slower strain rate, the HX phase of GaN partly nucleates and the untransformed regions are proved to be elastic deformed regions. Combined with an energy analysis, two atomic movement modes are recognized as the inducements for the phase transition and formation of elastic deformed regions. The first mode, which is responsible for the formation of elastic deformed regions, is an atomic sliding motion along the c {0001} planes. The second mode is a radial stretching atomic motion. The radial stretching motion, which requires a lot of energy, induces the WZ-HX phase transition. Moreover, the phase transition is affected drastically by the rise of temperature.
Highlights
Gallium nitride (GaN) has attracted a great deal of interest in industry, as a wide band gap material for numerous applications in optical and electronic devices.[1,2,3,4] Though extensive efforts have been made to investigate the practical performance of GaN, many fundamental questions remain
The simulation results of compression along the [0001] direction at a strain rate of 0.6373 ps-1 are shown in Fig. 2, where a complete transition was observed from the Wurtzite phase (WZ) phase to hexagonal phase (HX) phase
We investigate the solid-phase transition of GaN from the WZ phase to HX phase
Summary
Gallium nitride (GaN) has attracted a great deal of interest in industry, as a wide band gap material for numerous applications in optical and electronic devices.[1,2,3,4] Though extensive efforts have been made to investigate the practical performance of GaN, many fundamental questions remain. GaN possesses several phases providing dramatically different mechanical, electronic and optical properties. External stimuli, such as mechanical loading and pressure changes, can induce a transition between different phases. Little discussion has been conducted on this phenomenon in the current literature. This phase transition might be of importance in the future nanoscale application, such as the design and fabrication of flexible semiconductor devices. A series of compression simulations are conducted by the molecular dynamics method to investigate the atomic movement characteristic and mechanical response during the phase transition from WZ to HX of a GaN material
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