Selective area epitaxy

It should be noted that a reduction in the threading dislocation density in GaN has been achieved through the application of selective area epitaxy and lateral epitaxial overgrowth ((LEO), also known as epitaxial lateral overgrowth (ELO), or epitaxial laterally grown GaN (ELOG)). This epitaxial technique is discussed in Datareview B2.10 in this book. 

By using porous SiC substrates for GaN epitaxy, selective area epitaxy and lateral overgrowth can potentially be realized on these substrates without the need for any photolithography steps. Figure 5.2 shows a... 

Figure 4-40. Cross-sectional schematic of a selective area epitaxy (SAE) quantum wire structure.

Looking at the microstructure for samples above and below the maximum in coercivity, Fig. 21 shows that the FePt islands become interconnected above the coercivity maximum while below the maximum the islands are well separated. In the insets of Fig. 21(a) and (b) are the selected area diffraction (SAD) patterns for the samples. These indicate a single crystal FCT pattern with (001) orientation. Adjacent to the FePt diffraction spots are the (001) MgO single crystal spots indicating a slight mismatch in the lattice spacing of the two materials and a good epitaxial relationship between the two. 

B2.9 Selective area growth and epitaxial lateral overgrowth of GaN... 

Fabrication or InP/InAs/InP core-multishell heterostructure nanowire arrays shown in Fig. 24 has been achieved by selective area metal-organic vapour phase epitaxy.1 These core-multishell nanowires were designed to accommodate a strained InAs quantum well layer in a higher band gap InP nanowire. Precise control over the nanowire growth direction and the heterojunction formation enabled the successful fabrication of the nanostructure in which all the three layers were epitaxially grown without the assistance of a catalyst. 

Prior studies of selected area GaN epitaxy with reduced dislocation densities employed lithographically patterned substrates [4]. In contrast, this book describes a nonlithographic nanoscale surface patterning process. Dislocation reduction in epitaxial GaN growth without lithography, using discontinuous SiNx thin interlayers [5] is covered in Chapter 6. 

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