Epitaxial GaN layers synthesized on Si (111)

Abstract

Realization of epitaxial synthesis of high quality gallium nitride layers on silicon substrates is driven by the high potential of GaN-on-silicon technology for fabrication of high efficiency and relatively low-cost electronic devises. Growth process of GaN layers on Si substrates by molecular-beam epitaxy is complicated by differences in thermal expansion coefficients and lattice parameters causing large number of defects and dislocations. Another issue is mutual diffusion of Si and Ga. To improve the quality of GaN layers high temperature nitridation of silicon substrates was applied. We used Raman spectroscopy and Hall measurements to study the effect of nitridation. The shift of E2 H phonon mode allowed to calculate biaxial stress and this indicated stress relaxation in GaN epitaxial layers. P-type conductivity was observed in GaN/Si(111) structures and nitridation was proven to reduce carrier concentration. Thus, high temperature nitridation of Si substrate led to stress relaxation and decrease of Ga diffusion into substrate.