Determination of the Temperature Dependent Thermal Expansion Coefficients of Bulk AlN by HRXRD

Abstract

We measured the lattice constants of bulk aluminum nitride crystals at various temperatures by high resolution X-ray diffraction. By the use of a high temperature chamber and a X-ray cryostat a temperature regime from 20 to 1210 K was available. Furthermore, the measured data were fitted by Einstein-and Debye models which yield reliable parameters for the calculation of the thermal expansion coefficients of AlN.

Bulk AlN single crystal growth on foreign substrate and preparation of free-standing native seeds

“…The slightly reduced ''a'' lattice constant implies a small compressive strain in the grown crystals and likewise, the increased ''c'' lattice parameter indicates that the layers have a tensile strain along the growth direction. Nonetheless, these values show a fairly less lattice deformation when considering the lattice mismatch between AlN (a = 3.1111 Å) 23 and 4H-SiC (a = 3.0730 Å) 24 under the established crystal growth conditions. 3.2.2 CONFOCAL RAMAN MEASUREMENTS.…”

Influence of substrate temperature on the crystalline quality of AlN layers deposited by RF reactive magnetron sputtering

“…Edge-type dislocations were dominant in the AlN layer, with a density of 10 10 cm −2 estimated from a TEM image. The oxygen and carbon concentrations in the AlN layer were 7×10 20 and 2×10 20 atom·cm −3 , respectively. At a high sputtering power of 1000 W, the kinetic energy of sputtered Al atoms was reduced because of their collision, so the compressive stress in the AlN sputtered layer decreased.…”

“…7. The oxygen and carbon concentrations in the AlN layer were approximately 7×10 20 and 2×10 20 atom·cm −3 , respectively. The origin of the high oxygen and carbon concentrations might be residual or adsorbed gas in the sputtering chamber.…”

“…The TEM sample was prepared using a focused ion beam method. Two types of g/3g weak-beam dark-field TEM images taken near the AlN [11][12][13][14][15][16][17][18][19][20] zone axis with g = [10-10] and [0002] were obtained to determine the type of dislocation in the AlN sputtered layer. Here, g is a reciprocal lattice vector of the diffraction plane.…”

“…The lattice constants along the c-axis of the AlN layers sputtered at 823, 873 and 923 K were estimated to be 0.49886, 0.49901 and 0.49906 nm at room temperature, respectively, taking into account thermal strain. 20,21 Here, the in-plane thermal strain of the AlN layers was assumed to be equal to that of sapphire, and the unit cell volume of AlN was assumed to be constant. These estimated lattice constants are too small to explain those found experimentally (Fig.…”