Growth of crack-free GaN/Si heteroepitaxy by using a patterned Si substrate method

In this study, we describe a unique approach to the growth of near crack-free GaN single crystals by using periodically striped patterned Si(111), Prior to the growth of the crystals, the patterned Si(111) was fabricated with various patterned terrace sizes ranging from 17 to 120 μm by using a combination of a photolithography patterning technique and an inductively coupled plasma (ICP) etching method. GaN layers were grown on the Si substrates by using metalorganic chemical vapor deposition (MOCVD), and the technique is called the patterned Si substrate technique. We compared the quality of the GaN layer that was grown using patterned Si(111) with that of the layer that was grown using unpatterned Si(111). The crack density in the GaN layer on the patterned Si(111) was shown to be drastically reduced in comparison with that of the GaN layer on the unpatterned Si(111). The full width at half maximum (FWHM) values clearly decreased with decreasing patterned terrace size on the Si substrates. Moreover, the micro photoluminescence intensity at room temperature was found to increase with decreasing pattern size. Consequently, the patterned Si substrate technique is thought to not only improve the quality of the GaN layer but also reduce the tensile stress caused by the thermal and the lattice mismatches.