Formation and structure of inverted hexagonal pyramid defects in multiple quantum wells InGaN/GaN

Abstract

We have determined the structure of inverted hexagonal pyramid defects (IHPs) in multiple quantum wells InGaN/GaN by high-angle annular dark-field scanning transmission electron microscopy (HAADF STEM). HAADF STEM images reveal definitely that the IHP nucleates at a threading dislocation and grows in the form of a thin six-walled structure with InGaN/GaN {101̄1} layers. It has been found that IHPs start even at In-rich dots under adverse growth conditions.

Observation of V Defects in Multiple InGaN/GaN Quantum Well Layers

“…4(a) and (b). These images support very strongly the previous observations, 8,14,15) the images for which were somewhat obscure, and completely deny the model 11,12,16) that the main InGaN QWs end abruptly at the surfaces of the pits and the pits are then filled by the GaN capping layer with no InGaN/GaN sidewall layers. The InGaN and GaN sidewall layers were epitaxially grown successively on the six {10 1 11} planes during the MWQ deposition, each of them forming by the layer-by-layer growth similar to the growth on the (0001) planes.…”

“…For the analysis of the structure details of V defects, the present specimen with the thick QWs and barriers compares favorably with the In 0:2 Ga 0:8 N (2.5 nm)/ GaN (8 nm) MQW that was used in a previous experiments. 8,14,15) HAADF-STEM images give rise to strong contrast dependence on the atomic number so-called Zcontrast, unlike CTEM images.…”

“…They have the thin six-walled structure with InGaN/GaN {10 1 11} QWs which was proposed by Wu et al 13) This structure was first found in the In 0:2 Ga 0:8 N (2.5 nm)/GaN (8 nm) MQWs in a violet LD by HAADF-STEM 14) and confirmed in back-scattering electron images by fieldemission gun (FEG) scanning electron microscopy (SEM), 15) although some researchers have conjectured no InGaN/GaN sidewall layers. 11,12,16) Recently, Shiojiri et al 8) have discussed the formation mechanism of V defects.…”

Structural and optical properties of quaternary AlInGaN epilayers grown by MOCVD with various TMGa flows

“…Fig. 6 is a typical [10][11][12] cross-sectional dark-field TEM image of AlInGaN epilayer and underlying GaN template layer. It can be seen that each pit is associated with a threading dislocation from the underlying GaN template layer at its vertex.…”

Characteristics of Green Light-Emitting Diodes Using an InGaN:Mg/GaN:Mg Superlattice as p-Type Hole Injection and Contact Layers

“…While p-InGaN hole injection and contact layers are beneficial for the improvement of luminescence and electrical forward bias characteristics, the InGaN layer often shows, depending on thickness and composition of InGaN, a surface morphology with a high density of pits related to the formation of V-defects (also called inverted hexagonal pyramids), which have been proven to be associated with threading dislocations at their apexes. [9][10][11][12][13] It has been suggested that these pits act as a path for reverse leakage current. 14 In this study, in order to improve the surface morphology and electrical properties of the green LEDs, we developed an InGaN:Mg/GaN:Mg shortperiod superlattice (SPSL) to be used for p-type hole injection and contact layers.…”