Dielectric and Pyroelectric Properties of Composites Based on Aluminum and Gallium Nitrides Grown by Chloride-Hydride Epitaxy on a Silicon Carbide-on-Silicon Substrate

Abstract

We studied the microstructure and the dielectric and pyroelectric properties of Al x Ga 1 -x N composite epitaxial layers grown on SiC/Si(111) substrates by chloride-hydride epitaxy. The phenomenon of spontaneous (in the process of layer growth) formation of a system of heterojunctions was discovered. We obtained a material based on Al x Ga 1 -x N epitaxial layers, which currently has one of the highest pyroelectric coefficients for crystals (or thin films) of aluminum nitride.

Structure and properties of composites based on aluminum and gallium nitrides grown on silicon of different orientations with a buffer layer of silicon carbide

“…The analysis of formation of interlayers (or periodic AlGaN structure) observed before [24,25] shows that such structure is a result of composition self-organization and formation of a complex composite material that is apparently associated with periodic relaxation of mechanical stresses accumulated during heterostructure growth. It can be believed that the alteration of the composite material composition is accompanied with formation of heterojunctions and built-in space charge system; the latter shall severely affect the demonstration of dielectric and pyroelectric properties.…”

“…In the latter case, it is assumed that the use of substrates with another orientation may cause lower mechanical stresses in thin nitride layers and reduce the defect concentration. This, in turn, will allow to use epitaxial AlGaN layers to produce rather highresistivity heterostructures to enable the study of their polar properties [25]. The purpose of the research was to investigate the relationship between the polar properties and microstructure and composition of heterostructures based on epitaxial AlGaN layers grown on nanoscale SiC surface formed by the matched atom substitution method [8][9][10] on silicon substrates with two orientations, i.e.…”

Pyroelectric coefficient estimations for aluminum and gallium compounds

“…Let's discuss the findings of [26], which is focused on dielectric and pyroelectric properties of AlN-and GaNbased compounds grown by chloride-hybrid epitaxy on SiC/(111)Si substrate and where high PC values were obtained within (9−18) µC/m 2 • K, and the maximum value is observed for AlN/Al x Ga 1−x N structure with Al/N equal to 50.9/49.1.…”

“…(In this case an analogy with electrical conductance suggests itself, when instead of conductivity characterizing a homogeneous sample we have to imply conductance of a specific structure.) In [26], such structure is addressed as a composite material containing heterojunctions between the regions with different aluminum and gallium concentrations. It should be noted that similar, but chemically homogeneous banded structures (superlattices) have been detected before in epitaxial films of silicon carbide [27,28].…”

“…Moreover, high PC values can't be described only by the substrate effect using expression (5). Therefore, following the authors of [26], it should be assumed that heterojunctions are the main factors that determine the PC magnitude. The role of spontaneous polarization P s of hexagonal NH−SiC polytypes in formation of the energy-level diagram of 3C−SiC/NH−SiC/3C−SiC heterojunctions, where cubic 3C−SiC polytype has no spontaneous polarization, was addressed in [30].…”