Coordinated stress management and dislocation control in GaN growth on Si (111) substrates by using a carbon nanotube mask.

Abstract

A novel method is proposed to realize coordinated stress management and dislocation control in GaN growth on Si (111) substrates. This method is facilely implemented by using a unique carbon nanotube (CNT) mask with a nanoscale diameter and a high fill factor. It is found that most dislocations are directly blocked by high-density nanovoids formed around CNTs within 150 nm from the GaN/AlN interface. In this way, without dislocation inclination, the threading dislocation density (TDD) of the GaN epilayer is dramatically reduced. Thus the compressive stress relaxation due to dislocation inclination during GaN growth is significantly decreased and more compressive stress can be preserved. In addition, the high-density nanovoids also contribute to decreasing the thermal tensile stress during cooling down. As a result, coordinated stress management and dislocation control are realized and a 3.5 μm-thick crack-free GaN epilayer with a homogeneously low TDD of 2.51 × 108 cm-2 is obtained. With the facile fabrication of the CNT mask and a simple epitaxy procedure, the quality of the GaN epilayer grown on Si substrates is greatly improved, which extends the application of the nanomaterial in the GaN epitaxy on the Si substrate and demonstrates great application potential for high-performance electronic devices.