Temperature dependence of the thermal expansion of AlN

Abstract

The thermal expansion of wurtzite AlN bulk crystals grown by physical vapor transport was studied by high resolution x-ray diffraction in a temperature range from 20 to 1250 K. The temperature dependence of the derived anisotropic thermal expansion coefficients along the a- and c-directions could be well described over the entire temperature range within both the Debye model and the Einstein model. In comparison to GaN, larger expansion coefficients and higher characteristic temperatures have been found. The resulting thermal mismatch of AlGaN/GaN heterostructures are presented.

Low temperature AlN growth by MBE and its application in HEMTs

“…In this experiment, the thickness of the AlN films grown on GaN was larger than the critical thickness. AFM images show cracks on the surface of the 15 nm AlN layers grown at T Tc $ 800, 660 and 470 1C [10]. Based on their hypothesis, the mismatch between the in-plane lattice constants of AlN and GaN induced only by thermal expansion is maximum ( $0.055%) at a temperature of $ 700 K (427 1C).…”

The effect of interlayer composition and thickness on the stabilization of cubic AlN in AlN/Ti–Al–N superlattices

“…Although there are several reports on volume and pressure dependences of elastic constants and thermal expansion of carbides and nitrides [50], including w-AlN [51], these material constants are not available for the whole compositional range of c-Ti 1-x Al x N. Hence in the current study, we use exclusively DFT predictions corresponding to 0 K, which are known to be reliable estimates for the room Table 1 Surface energies of differently oriented facets of c-and w-AlN (taken from Ref. [37] …”

Intersubband transitions in nonpolar GaN/Al(Ga)N heterostructures in the short- and mid-wavelength infrared regions

“…30,31 For the samples in this study, it appears that these defects do not develop during the growth, but instead during the cooling process as a result of the temperature-dependent GaN/AlN lattice mismatch. 32 On the AFM scale, the root-mean-square (rms) surface roughness measured in images of an area of 5×5 µm 2 was 1.1±0.2 nm, 2.0±0.6 nm, and 3.7±1.2 nm for c-, m-, and a-plane samples, respectively, i.e. m-plane growth systematically resulted in smoother surfaces than a-plane growth.…”