Study of Edge and Screw Dislocation Density in GaN/Al2O3 Heterostructure

Abstract

This study assesses the characteristics (edge and screw dislocation density) of a commercially available GaN/AlN/Al2O3 wafer. The heterostructure was evaluated by means of high-resolution X-ray diffraction (HR-XRD), high-resolution transmission electron microscopy (HR-TEM), and Doppler-Broadening Spectroscopy (DBS). The results were mathematically modeled to extract defect densities and defect correlation lengths in the GaN film. The structure of the GaN film, AlN buffer, Al2O3 substrate and their growth relationships were determined through HR-TEM. DBS studies were used to determine the effective positron diffusion length of the GaN film. Within the epitaxial layers, defined by a [GaN P 63 m c (0 0 0 2) || P 63 m c AlN (0 0 0 2) || (0 0 0 2) R 3 ¯ c Al2O3] relationship, regarding the GaN film, a strong correlation between defect densities, defect correlation lengths, and positron diffusion length was assessed. The defect densities ρ d e = 6.13 × 1010 cm−2, ρ d s = 1.36 × 1010 cm−2, along with the defect correlation lengths Le = 155 nm and Ls = 229 nm found in the 289 nm layer of GaN, account for the effective positron diffusion length Leff~60 nm.

Studies of Defect Structure in Epitaxial AlN/GaN Films Grown on (111) 3C-SiC

“…The results which summarize the characteristics of the GaN layers listed in this study along with previously reported results [ 13 , 14 ] are shown in Table 2 . Additionally, Figure 4 c,d show the omega scans for (0004) and ( ) planes for GaN films grown on (111) 3C-SiC, (0001) Al 2 O 3 , and (111) Si substrates [ 13 , 14 ].…”

“…Our attempts to fit the experimental data using a three-layer model resulted in physically incorrect data, so a four-layer model was proposed instead, thereby splitting the GaN film into two sublayers (i.e., GaN1 and GaN2). A detailed explanation why the three-layer model results are incorrect is given in references [ 13 , 14 ].…”

“…The GaN/SiC sample used in this work with dimensions of 10 × 10 × 0.35 mm 3 was produced at the NTT Advanced Technology Corporation (Kanagawa, Japan) for high-electron-mobility transistors. As presented in our previous work [ 13 , 14 ], the wafers’ exact growth conditions were not made available by the producer.…”

“…Our previous studies revealed some differences in the influence of lattice mismatch between the substrates and the AlN/GaN layers [ 13 , 14 ]. However, the mechanisms through which the buffer layer relieves stress and how this consequently affects defect formation are difficult to control.…”

Dynamics Studies of Nitrogen Interstitial in GaN from Ab Initio Calculations

“…However, in the process of GaN growth, the large lattice mismatch of GaN with its substrate (silicon carbide (SiC) or sapphire) is inevitable. In addition, there are varieties of defects appearing in the whole fabrication process, including native point defects and impurities, such as C, O, H, as well as dislocations [ 7 , 8 ]. Therefore, it is still a big challenge to improve the performance of GaN-based devices.…”