Goutam Kumar Dalapati; Vignesh Suresh; Sandipan Chakraborty; Chandreswar Mahata; Yi Ren; Thirumaleshawara Bhat; Sudhiranjan Tripathy; Taeyoon Lee; Lakshmi Kanta Bera; Dongzhi Chi
Abstract
The structural defects and formation of native oxides during thermal treatment on p-type epitaxial-GaAs/Ge have been investigated using spectroscopic measurements and electrical characterization. The performance of epi-GaAs based device depends on the interface quality between epi-GaAs and gate oxide ...
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The structural defects and formation of native oxides during thermal treatment on p-type epitaxial-GaAs/Ge have been investigated using spectroscopic measurements and electrical characterization. The performance of epi-GaAs based device depends on the interface quality between epi-GaAs and gate oxide and structural quality of the epi-GaAs layer. P-type epitaxial-GaAs was grown on Ge substrate using MOCVD technique at 675oC. Defective surface native oxides of arsenic and gallium oxides are observed for as-grown epi-GaAs layer. The arsenic oxide significantly reduced after thermal treatment as seen from XPS observations. The structural defects at surface enhanced after thermal treatment which is clearly probed by micro-Raman spectroscopy. Atomic layer deposited (ALD) Al2O3 significantly improved the interface properties after thermal treatment compared with bare epi-GaAs layer. Even though, the interface trap defect density slightly higher for p-type epi-GaAs MOS capacitor compared with bulk p-type GaAs devices, high frequency-dispersion in epi-GaAs based devices observed. This is mainly governs through the formation of p-i-n junction diode in the epi-GaAs layer on Ge substrates.
Anindita Das; Sanatan Chattopadhyay; Goutam Kumar Dalapati
Abstract
In the current work, electrical performance of n-channel GaAs MOSFETs with HfO2 gate dielectrics has been investigated by considering the impact of oxygen diffusion from gate dielectric layer. Initially, the HfO2/GaAs MOS capacitors are fabricated and its relevant process recipe has been simulated. The ...
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In the current work, electrical performance of n-channel GaAs MOSFETs with HfO2 gate dielectrics has been investigated by considering the impact of oxygen diffusion from gate dielectric layer. Initially, the HfO2/GaAs MOS capacitors are fabricated and its relevant process recipe has been simulated. The key parameters are extracted from both the experimental and simulated results to calibrate the simulator. The extracted parameters are subsequently fed into the simulator to investigate electrical performance of n-channel GaAs MOSFETs with varying gate lengths. The elemental diffusion of oxygen at HfO2/GaAs interface has also been incorporated since oxygen naturally diffuses into the GaAs layer during deposition and annealing steps and thereby alters the effective doping concentration in the channel. The diffused oxygen has been observed to improve electrical performance parameters such as transconductance and threshold voltage, however, degrades DIBL of the HfO2/GaAs MOSFET devices.
S. M. Mamand; M. S. Omar; A. J. Muhammed
Abstract
Theoretical calculations of the magnitude and temperature variation of the measured thermal conductivity of undoped and doped GaAs nanobeams will present. The calculations have been performed by employing modified Callaway’s theoretical model. In the model, both longitudinal and transverse modes ...
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Theoretical calculations of the magnitude and temperature variation of the measured thermal conductivity of undoped and doped GaAs nanobeams will present. The calculations have been performed by employing modified Callaway’s theoretical model. In the model, both longitudinal and transverse modes are explicitly taken into account. Scattering of phonons is assumed to be by nanobeam boundaries, imperfections, dislocations, electrons, and other phonons via both normal and Umklapp processes. A method is used to calculate the Debye temperature and phonon group velocities for undoped and doped nanobeams from their related melting points. Phonon confinement and size effects as well as the role of dislocation in limiting thermal conductivity are investigated. The drop in thermal conductivity of doped nanobeams compared to that of the undoped beams arises from electron-phonon scattering and additional phonon scattering from a large number of point impurities due to the presence of dopant atoms. Effect of Gruneisen parameter, surface roughness, and dislocations are successfully used to correlate the calculated values of lattice thermal conductivity to that of the experimentally measured curves.
