Growth of high quality a-plane GaN epi-layer on r-plane sapphire substrates with optimization of multi-buffer layer

Characterization of deep levels in a-plane GaN epi-layers grown using various growth techniques

“…This intermediate layer was expected to reduce the density of threading dislocations, and the growth temperature of the third buffer layer increased to 1160 1C. These optimized growth conditions were verified in our previous report [11]. For the second sample (sample II), in-situ SiN x interlayer was additionally inserted in between the second and the third buffer layers of the modified two-step growth layers.…”

“…1(a) shows the crosssectional and plan-view (inset) TEM images of sample I with two-beam conditions. For the cross-sectional TEM image viewed along the c-direction of sample I, partial dislocations (b ¼ 1/5o20-234) and several types of threading dislocations could be observed with the two beam condition of g ¼ [11][12][13][14][15][16][17][18][19][20]. Threading dislocations were formed at the interface between the substrate and the GaN layer, and it was shown that the majority of the defect lines starts to change direction from (1-100) to (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) by the layer transition between three and two dimensional growth layers.…”

“…In this study, we have carried out a detailed investigation of the defects in a-plane GaN films by transmission electron microscopy (TEM) and deep level transient spectroscopy (DLTS) of three samples employing various growth techniques, which are modified two-step growth [11], SiN x interlayer, and epitaxy on patterned insulator on sapphire substrate (EPISS). Threading dislocation densities in samples were estimated by TEM images with two-beam conditions.…”

“…Cross-sectional and plan-viewed (insets) TEM images of the samples I, II, and III: (a) For sample I, cross-section of the sample was viewed along (0001) with g¼[11][12][13][14][15][16][17][18][19][20], and plan-view image of the inset was taken with g ¼[0002]. (b) Crosssectional TEM image of sample II using SiN x interlayer was viewed along (0001) with g ¼[11][12][13][14][15][16][17][18][19][20].…”

“…(b) Crosssectional TEM image of sample II using SiN x interlayer was viewed along (0001) with g ¼[11][12][13][14][15][16][17][18][19][20]. Inset showed plan-view image with a two-beam condition of g¼ [0002].…”