Lattice distortions in GaN thin films on (0001) sapphire

Rao, D.V. Sridhara; Beanland, Richard; Kappers, Menno J.; Zhu, Dandan; Humphreys, C. J.

doi:10.1088/1742-6596/209/1/012022

Cited by 2 publications

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“…It is to be noted that the c-plane GaN has very large lattice mismatch with Si, sapphire and the associated strain relaxation manifests in GaN films in the form of high density of microstructural defects, viz., misfit dislocations (MDs), threading dislocations (TDs), inversion domains (IDs), V-defects, etc. The electron microscopy methods, viz., weakbeam dark field imaging (WBDF), convergent beam electron diffraction (CBED), electron back scattered diffraction (EBSD), electron-energy loss spectroscopy and EDS methods are suitable for the detailed investigation of microstructural and compositional aspects [16][17][18][19][20][21][22][23][24][25] and the micro details are given in a detailed technical report 26 . These techniques have been applied for the study of these microstructural issues in GaN films.…”

Section: Gan Hemt Device Structuresmentioning

confidence: 99%

Microstructural and Compositional Characterisation of Electronic Materials

et al. 2016

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Microstructural and compositional characterisation of electronic materials in support of the development of GaAs, GaN and GaSb based multilayer device structures is described. Electron microscopy techniques employing nanometer and sub-nanometer scale imaging capability of structure and chemistry have been widely used to characterise various aspects of electronic and optoelectronic device structures such as InGaAs quantum dots, InGaAs pseudomorphic (pHEMT) and metamorphic (mHEMT) layers and the ohmic metallisation of GaAs and GaN high electron mobility transistors, nichrome thin film resistors, GaN heteroepitaxy on sapphire and silicon substrates, as well as InAs and GaN nanowires. They also established convergent beam electron diffraction techniques for determination of lattice distortions in III-V compound semiconductors, EBSD for crystalline misorientation studies of GaN epilayers and high-angle annular dark field techniques coupled with digital image analysis for the mapping of composition and strain in the nanometric layered structures. Also, in-situ SEM experiments were performed on ohmic metallisation of pHEMT device structures. The established electron microscopy expertise for electronic materials with demonstrated examples is presented. Keywords:Electronic materials, semiconductor electronic device, nanowires, infrared device structure REVIEW ARTICLE DEf. SCI. J., VOl. 66, NO. 4, July 2016 342 techniques for quantitative lattice distortion studies in III-V thin films & polarity of GaN based films 5,6 (e) quantitative strain/compositional studies of epitaxial thin films by the digital analysis of HRTEM images 7(f) quantitative analysis of heterointerfaces by atomic-column ratio mapping (g) in-situ SEM studies, and (h) compositional analysis by EDS and EELS techniques.An overview of GaAs, GaSb and GaN multilayer semiconductor device structures and the application of advanced electron microscopy techniques to study various issues in these materials development programs are presented. GaAs HEMt dEVIcE StructurESHEMT is a field effect transistor in which the channel is a quantum well (QW) realised by embedding a narrow bandgap semiconductor (such as InGaAs) between two wide bandgap semiconductors (e.g., GaAs and AlGaAs) and the carriers (two-dimension electron gas, 2DEG) in channel are populated by modulation doping.GaAs devices are made as pHEMTs (pseudomorphic HEMTs) and mHEMTs (metamorphic HEMTs). The schematics of these devices are shown as Fig. 1. It is to note that the increase of indium content in the In x Ga 1-x As channel enhances the saturation velocity and mobility of carriers, hence for given HEMT device features (for example, gate length), mHEMT has highest f T (the gain of the device is measured as a function of frequency, it decreases with frequency and reaches to unity at f T ), which is desirable for the device applications.grading by varying the indium content. In this case, misfit dislocations can originate and propagate as threading dislocations in the overgrown epilayers, if...

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Section: Gan Hemt Device Structuresmentioning

confidence: 99%

Microstructural and Compositional Characterisation of Electronic Materials

et al. 2016

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Cross-correlation based high resolution electron backscatter diffraction and electron channelling contrast imaging for strain mapping and dislocation distributions in InAlN thin films

et al. 2017

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We describe the development of cross-correlation based high resolution electron backscatter diffraction (HR-EBSD) and electron channelling contrast imaging (ECCI), in the scanning electron microscope (SEM), to quantitatively map the strain variation and lattice rotation and determine the density and identify dislocations in nitride semiconductor thin films. These techniques can provide quantitative, rapid, non-destructive analysis of the structural properties of materials with a spatial resolution of order of tens of nanometers. HR-EBSD has a sensitivity to changes of strain and rotation of the order of 10−4 and 0.01° respectively, while ECCI can be used to image single dislocations up to a dislocation density of order 1010 cm−2. In the present work, we report the application of the cross-correlation based HR-EBSD approach to determine the tilt, twist, elastic strain and the distribution and type of threading dislocations in InAlN/AlN/GaN high electron mobility transistor (HEMT) structures grown on two different substrates, namely SiC and sapphire. We describe our procedure to estimate the distribution of geometrically necessary dislocations (GND) based on Nye-Kroner analysis and compare them with the direct imaging of threading dislocations (TDs) by ECCI. Combining data from HR-EBSD and ECCI observations allowed the densities of pure edge, mixed and pure screw threading dislocations to be fully separated

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Lattice distortions in GaN thin films on (0001) sapphire

Cited by 2 publications

References 10 publications

Microstructural and Compositional Characterisation of Electronic Materials

Microstructural and Compositional Characterisation of Electronic Materials

Cross-correlation based high resolution electron backscatter diffraction and electron channelling contrast imaging for strain mapping and dislocation distributions in InAlN thin films

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