Origin of faceted surface hillocks on semi-polar View the MathML source GaN templates grown on pre-structured sapphire

Highlights

We provide a detailed TEM characterization of semi-polar (1 1 −2 2) GaN templates grown on pre-structured r-plane sapphire by MOVPE followed by HVPE.
Regions associated with the coalescence event during the MOVPE growth are still highly faulted, acting as a source of dislocations and stacking faults in the HVPE process.
Surface hillocks appear due to the formation inversion domains underneath.
Inversion domains are formed as a result of the existence of randomly oriented GaN particles at the coalescence regions at the HVPE/MOVPE interface.

Abstract

The microstructure of semi-polar View the MathML source GaN templates grown on pre-structured r-plane sapphire by metal–organic vapor phase epitaxy (MOVPE) followed by hydride vapor phase epitaxy (HVPE) has been characterised by transmission electron microscopy (TEM). It is found that dislocations originating from the inclined c-plane-like GaN/sapphire interface bend and then terminate either at the coalescence regions of the adjacent GaN stripes or at the SiO2 mask. However, the regions associated with the coalescence event during the MOVPE growth act as a source of dislocations and stacking faults in the subsequent growth process. More importantly, a direct link between the formation of a surface hillock, the presence of an inversion domain, and the preferential nucleation of randomly oriented GaN particles at a region containing a dislocation bundle originating from coalescence has been established. It is suggested that controlling the surface conditions of the MOVPE GaN layer before HVPE and optimising the HVPE nucleation process are important to avoid the surface hillocks.

Keywords

  • A1. Characterization
  • A1. Defects
  • A3. Hydride vapor phase epitaxy
  • A3. Metalorganic vapor phase epitaxy
  • B1. Nitrides
  • B2. Semiconducting III–V materials                                                                                                                                                                                                                                                  
  • Source:Sciencedirect 

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