Lateral overgrowth mechanisms and microstructural characteristics of bulk-like GaN layers grown by sublimation method

The selective overgrowth method has been used to grow bulk-like GaN layers by sublimation method. Si and SiO2, which have a different evaporation rate, thermal conductivity, and thermal expansion coefficient, have been chosen as mask materials. The effect due to the reduction of dislocation density with different mask materials has been discussed. The lateral growth rates strongly depend on the direction of the mask stripe. For the stripe windows aligned in GaN〈1100〉 direction, the lateral growth rate is approximately four times higher than with stripe direction in GaN〈1120〉. The microstructure of selectively regrown GaN has been investigated by transmission electron microscopy, scanning electron microscopy, and cathodoluminescence to understand the lateral growth mechanisms in sublimation. The threading dislocations in the region of laterally regrown GaN are extended in two different ways. First, the threading dislocations are perpendicularly propagated into the top surface in the window region. In thi...