Anisotropy of Strain Relaxation in III-V Semiconductor Heterostructures

Abstract

Partially relaxed III–V heterostructures: GaAs/InGaAs and InP/InAlAs/InGaAs, with a small lattice mismatch, grown using molecular beam epitaxy under compressive or tensile misfit stress at the (001) interface, have been investigated by means of high-resolution X-ray diffractometry, atomic force microscopy and generalized ellipsometry. Additionally, transmission electron microscopy and electron-beam induced current in a scanning electron microscope have been employed to reveal misfit dislocations at the heterostructure interface. Chemical etching was used to determine polarity of the crystals and threading dislocation densities in the epitaxial layers. Our findings are interpreted in terms of the dependent on growth conditions, material’s composition and doping glide velocities of two types of misfit dislocations: α and β, differing in their core structure and lying along two orthogonal 〈110〉 crystallographic directions at the (001) interface.

Strain relaxation induced surface morphology of heterogeneous GaInNAs layers grown on GaAs substrate

“…dislocation nucleation and glide. As a consequence, the asymmetric 2D network of  and  dislocations, running in two perpendicular 110 directions is usually formed, resulting in anisotropic misfit strain relaxation of the epitaxial layer in these directions [11][12][13][14][15][16][17]. Indeed, our previous studies on the GaInNAs/GaAs heterostructure showed a distinct anisotropy of strain relaxation related to the asymmetry in formation of interfacial dislocation network [8].…”

“…The cross-hatch surface morphology is usually recognized to be directly related with strain relaxation via threading dislocation glide which results in both surface step and misfit dislocation formation [9,10]. Such a morphology is often observed during strain relaxation in many III-V lattice mismatched semiconductor systems, such as GaInAs/GaAs [11,12] or GaNAs/GaAs [13,14].…”

“…As it was already mentioned, the presence of MDs network at the interface can also cause undulating surface morphology, known as a cross-hatch pattern, in the form of linear 'scratches' oriented along two perpendicular 〈 〉 crystallographic directions on the (001) epitaxial layer surface [18]. In order to distinguish between these two 〈 〉 directions on the surface, selective chemical etching was used, according to the procedure described in Ref [11].…”

Inhomogeneity-mediated systematic reduction of the Schottky barrier in a Au/GaN nanorod film interface

“…Most of these devices are based on thin films and grown epitaxially on limited lattice-matched substrates such as Al 2 O 3 , Si (111), GaN bulk, etc. However, even a slight lattice mismatch between the substrate and the grown films induces significant strain [15][16][17][18], which is generally relaxed through physical defect formation (threading dislocations, basal plane stacking faults, slip planes, etc [19][20][21][22]), but these defects significantly affect device performance [23][24][25][26][27]. Au is used for making electrode patterns on III-nitride-based devices because of its exceptional electrical properties; however, it makes a Schottky contact with GaN thin films, which is extremely important for some devices like diodes, photodetector, switches, etc, for the effective transport/separation of charge carriers.…”