Crystalline property analysis of semipolar (20–21) GaN on (22–43) patterned sapphire substrate by X‐ray microdiffraction and transmission electron microscopy

Abstract

We have investigated the microscopic crystalline morphology such as lattice plane tilting and defects in semipolar (20–21) GaN films grown on (22–43) patterned sapphire substrates (PSS) by using position‐dependent ω–2θ map measurement of X‐ray microdiffraction (XRMD) combined with transmission electron microscopy (TEM). The results of the position‐dependent ω–2θ map measurement for the GaN (20–21) plane showed periodic variation of the diffraction spot shapes depending on the patterning pitch of the PSS. Broadening of the diffraction spots in the terrace area and single diffraction spots in the grooved one were also observed. These results indicate that the lattice plane tilting of the GaN film depends on the PSS structure and the presence of the defective GaN film on the terrace area where basal plane stacking‐fault generation occurred, as confirmed by TEM.

Thickness and growth condition dependence of crystallinity in semipolar (20–21) GaN films grown on (22–43) patterned sapphire substrates

“…This is because the semipolar (20)(21) GaN can suppress the piezoelectric polarization, which often induces the reduction of the luminous efficiency in InGaN/GaN quantum wells. Currently, the (20)(21) GaN template is available only by slicing bulk c-plane GaN crystals, meaning that the size of the template is limited. Hence, large size (20)(21) GaN templates with high crystalline quality is strongly demanded.…”

“…1 Introduction Semipolar (20)(21) GaN is one of the most promising planes of GaN substrates for fabricating green laser diodes and light emitting diodes [1,2]. This is because the semipolar (20)(21) GaN can suppress the piezoelectric polarization, which often induces the reduction of the luminous efficiency in InGaN/GaN quantum wells.…”

“…Currently, the (20)(21) GaN template is available only by slicing bulk c-plane GaN crystals, meaning that the size of the template is limited. Hence, large size (20)(21) GaN templates with high crystalline quality is strongly demanded. In order to obtain the (20-21) GaN template with large size and high crystalline quality, epitaxial growth techniques on foreign substrate such as sapphire must be developed by using metalorganic vapor phase epitaxy (MOVPE) combined with hydride vapor phase epitaxy (HVPE).…”

“…For the (20)(21) GaN epitaxial growth, (22-43) patterned sapphire substrates (PSS) has been effectively used as the template [3][4][5][6][7][8]. The (22-43) PSS has periodic terrace/trench structure with a few micron in width and depth.…”

“…As continuing the epitaxial growth process, the GaN film laterally grows over the terrace and coalesces into growing GaN film coming from next trench. Finally, the continuous (20)(21) GaN film can be obtained on the (22-43) PSS.…”