Pendeo-epitaxial Layers

Application of Pendeo-epitaxy for the Layers Crown on Nonpolar Substrates 

Ga-polarity (b) the seed area and (c) the wing grown with N-polarity. Note a substantial deviation (tilt and twist) in (b) and (c) compared to (a) area. 

Application of Lateral Overgrowth for a-plane GaN Layers Crown on the r plane of AI2O3 

Bending contours are due to bending of thin TEM sample. Note some defects (mainly stacking faults) present in the Ga-wing (vertical lines). 

Ga-polar direction. However, by adjusting the growth parameters (two-step growth), the Ga-polarity to N-polarity wing ratio can be as low as 3 1 and the sample surface is flat, as desired for application of this material in devices. 

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Figure 10.18 Schematic diagrams of the pendeo-epitaxial layers. Vertical lines indicate defects in the seed area propagating to the sample surface.

Defects Formed in Nonpolar CaN Grown on SiC and AI2O3 and their Reduction in Pendeo-epitaxial and Laterally Overgrown GaN Layers... 

Since optoelectronic properties of GaN-based devices strongly depend on the structural quality of the heterostructure layers, the first part of this chapter will discuss the defects formed in GaN -plane layers grown on nonpolar (1120) 4H-SiC. In the second part of this chapter, pendeo-epitaxial and laterally overgrown epitaxial layers will be characterized and possible defect reduction using these methods will be discussed. Transmission electron microscopy (TEM) methods will be used to characterize these defects. 

Figure 10.19 Cross-section micrograph from the pendeo-epitaxial GaN layer showing defect distribution over the seed and in the wings. Note the uniform contrast indicating that the misorientation in this sample is small.

Figure 10.20 TEM micrograph of a cross-section uncoalesced pendeo-epitaxial GaN layer grown on o-plane 4H SiC. High density of defects (mainly stacking faults (SFs) and dislocations) is observed in the seed area (b) CBED pattern taken in the...

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