Hydride vapor phase epitaxy 법을 이용하여 Si(111)기판 위에 성장한 SAG-GaN의 특성에 관한 연구

Abstract

GaN is used in high-temperature/high-power devices, light emitting diodes (LEDs) and laser diodes (LDs) in the short wavelength region due to its unique properties. However, due to the lack of suitable low-cost substrates for homoepitaxy,the growth of GaN films is usually performed on sapphire or SiC substrates.

However, the insulating properties and extreme hardness of sapphire substrates, the small available sizes and expense of SiC substrates make difficulties for device fabrication. On the other hand, silicon is regarded as a relatively promising substrate for GaN epitaxy because it offers the advantages of low cost, large area, high thermal conductivity and integration with well-established Si processing.

Unfortunately, cracking due to large thermal mismatch, melt-back etching and SixNy layer formation at the beginning of growth means that GaN grown on Si substrates has a higher threading dislocation density than that on sapphire and SiC substrates.

However, the selective area growth (SAG) technique and the epitaxial lateral overgrowth (ELO) technique have been reported to considerably reduce the dislocation density in GaN. Recently SAG by hydride vapor phase epitaxy (HVPE) and metal organic chemical vapor deposition (MOVPE) methods have been reviewed and various methods were applied to the growth of GaN on a silicon substrate. SAG is a very useful technique for the fabrication of micro-structures and semiconductor devices and also helps the understanding of growth mechanisms.

Many research groups have performed SAG experiments using SiO2 masks on sapphire or SiC substrates and have reported on the growth facet control and dislocation density.

The purpose of this study is to investigate the properties of SAG-GaN by hydride vapor phase epitaxy (HVPE). It has been performed on SiO2 stripe-maskpatterned Si(111) substrates with various epi-layers. AlGaN, GaN and AlN epi-layer were used as buffer layers. The orientation of the SiO2 mask pattern was opened along the Si <-110> direction. The properties of the SAG-GaN samples were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD),atomic force microscopy (AFM) and photoluminescence (PL). SEM images show that hexagonal SAG-GaN grows vertically along the <0001> direction,longitudinally along the <11-20> direction with facets on the sidewall growing along (1-101) the direction. The PL spectra show band edge emission peaks.