Strain Modification of GaN in AlGaN/GaN Epitaxial Films

Abstract

We investigated AlGaN/GaN heterostructures grown by metal-organic vapor-phase epitaxy on sapphire by calorimetric absorption, transmission and reflection spectroscopy (CAS/CTS/CRS) at 47 mK. The AlGaN film on a 2-µm-thick GaN layer introduces additional compressive strain into the GaN layer. A blue shift of the A-and B-exciton line positions is directly proportional to the AlN molar fraction in the films. The amount of strain in the GaN layers is quantified by micro-Raman experiments. We can explain the results by taking into account the elastic properties of GaN and AlGaN.

Nanostructural characterization and two-dimensional electron-gas properties in high-mobility AlGaN∕AlN∕GaN heterostructures grown on epitaxial AlN/sapphire templates

“…Figure 4 shows the crosssectional FFTM images obtained by analyzing a highresolution TEM image taken around the AlGaN / AlN / GaN interfaces for the same sample as that shown in Fig. In this table, prospective lattice constants, 13,14 which were estimated assuming that the AlGaN and AlN layers are coherently strained on the underlying GaN layer, are also shown. Figures 4͑a͒ and 4͑b͒ show the distributions of the axial͓0002͔ and in-plane ͓0110͔ lattice spacings, respectively.…”

Propertiesofstrainedzinc-blendeGaN:first-principlesstudy

“…This is related to the large lattice mismatch and the difference in the thermal expansion coefficients between epitaxial layer and substrate, which can cause large stresses in the epitaxial layers. In the case of the heterostructures and superlattices, this situation become more complex and mutual influence between different material layers may appears [9,10]. Whereas investigations of strain effects have been widely published for the electronic and optical properties [9][10][11][12][13][14], much less is known about their influence on the elastic constants, energy band information depending on a strain, and bonding nature as well as ionicity factor under pressure.…”

Photoluminescence Investigations of AlGaN on GaN Epitaxial Films

“…In the inset the increase in donor binding energy as a function of the Al-content is shown assuming Hayne's rule is valid in AlGaN model (neglecting thermal mismatch) and taking into account the elastic constants of Al x Ga 1Àx N (interpolating between GaN and AlN). Details are published in [15].…”