Influence of edge-grown HVPE GaN on the structural quality of c-plane oriented HVPE-GaN grown on ammonothermal GaN substrates

Defects in Single Crystalline Ammonothermal Gallium Nitride

“…[9] The origin of bowing is linked with in-plane dislocations, [13] inclination of dislocations, [4] and non-uniform growth at wafer edges. [14,15] The resulting radius of curvature of HVPE grown quasi-bulk substrates is commonly below 10 m and results in inclined lattice planes and complicates subsequent polishing and epitaxial steps. [4] Lower bow values has been reported for HVPE material grown on SI substrates with an in-situ substrate removal process.…”

“…This is most likely due to unstable growth of the a-planes which have been reported to convert to inclined planes during growth. A post growth analysis of the a-wing side wall angle suggests that the growth direction transforms to [11][12][13][14][15][16][17][18][19][20][21][22] [40] (as shown in Figure 4) or [10][11] [74] at some point during the growth process. The presence of several growth facets leads to non-uniform growth and impurity incorporation in the a-wing region.…”

“…The effects of stress generated by different impurity incorporation in wing and seed regions have been recently studied in HVPE grown GaN. [14,15] The lattice constant of wing regions grown in semi-and nonpolar directions was found to differ significantly from the seed region grown in c-direction resulting in large tensile stress in the seed region. The stress was high enough to cause defect generation and plastic deformation after the crystal reached a critical thickness.…”

“…This subsequently limits the size of nonpolar and semipolar substrates obtained by HVPE grown crystals . The origin of bowing is linked with in‐plane dislocations, inclination of dislocations, and non‐uniform growth at wafer edges . The resulting radius of curvature of HVPE grown quasi‐bulk substrates is commonly below 10 m and results in inclined lattice planes and complicates subsequent polishing and epitaxial steps .…”

GaN Single Crystalline Substrates by Ammonothermal and HVPE Methods for Electronic Devices

“…The reason for this is a different incorporation of dopants (mainly oxygen) into HVPE-GaN grown in the [0001] than in lateral directions. This leads, in turn, to different lattice parameters of the crystallized material [23,51,52]. The stress from the edges is much more significant than the one generated by the lattice mismatch between the seed and the deposited layer.…”