Cathodoluminescence of GaInN quantum wells grown on nonpolar a plane GaN: Intense emission from pit facets

Abstract

Ga x In 1−x N quantum wells grown by metal organic vapor phase epitaxy on a plane GaN grown on r plane sapphire substrate typically show relatively large surface pits. We show by correlation of low temperature photoluminescence, cathodoluminescence, scanning and transmission electron microscopy that the different semipolar side facets of these pits dominate the overall luminescence signal of such layers.

Morphology and origin of V-defects in semipolar (11–22) InGaN

“…For this purpose we considered the facet orientations that have been reported in the literature. All information regarding facets so far comes either from the polar c-plane or nonpolar a-plane and m-plane growths [12][13][14]17]. Moreover, in the case of a-plane films, the pits reported so far are of much larger size than in our case.…”

“…This understanding is crucial towards obtaining template surfaces suitable for deposition of nanostructures. In nonpolar a-plane GaN, large triangular pits with sizes of several micrometers have been reported in epilayers grown on r-plane sapphire by metalorganic vapor phase epitaxy (MOVPE) [12][13][14]. However, such pits have been attributed to the island coalescence during growth.…”

“…This has been attributed to a modification of the surface energy in the presence of indium, and it is interesting to examine if a correlation between structural defects and surface pits can be established similar to the polar case. Furthermore, the morphology of surface pits is crucial, both for determining the indium incorporation efficiency in the semipolar orientations [15], as well as for influencing the emissive properties [12].…”

Growth and coalescence behavior of semipolar $(11{\bar {2}}2)$ GaN on pre‐structured r‐plane sapphire substrates

“…Nonpolar a-plane GaN could be grown directly on r-plane sapphire [3,4], whereas nonpolar m-plane GaN was grown on various substrates like Al 2 O 3 [5], LiAlO 2 [6], or SiC [7]. However, all of these approaches suffer from inferior material quality, which is noticeable by a high number of (basal plane) stacking faults ((B)SF)s [8] or morphological defects [9] which negatively influence the performance of the subsequent devices. A third approach to get in particular semipolar devices is to use facets of coriented grown GaN on structured GaN templates [15].…”

“…The nonpolar directions are perpendicular to the c-direction with no piezoelectric fields present along the growth direction. In particular, the ð1120Þ a-and ð1010Þ m-directions have been investigated intensively [3][4][5][6][7][8][9]. Semipolar directions lie between the cdirection and the nonpolar directions.…”