اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدSurface optical phonon scattering in N-polar GaN quantum well channels
118
0
0.0
(
0
)
تأليف
Uttam Singisetti
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
N-polar GaN channel mobility is important for high frequency device applications. In this Letter, we report the theoretical calculations on the surface optical (SO) phonon scattering rate of two-dimensional electron gas (2-DEG) in N-polar GaN quantum well channels with high-k dielectrics. The effect of SO phonons on 2-DEG mobility was found to be small at >5 nm channel thickness. However, the SO mobility in 3 nm N-polar GaN channels with high-k dielectrics is low and limits the total mobility. The SO scattering for SiNx dielectric GaN was found to be negligible due to its high SO phonon energy.
قيم البحث
اقرأ أيضاً
We investigate the radiative and nonradiative recombination processes in planar (In,Ga)N/GaN(0001) quantum wells and (In,Ga)N quantum disks embedded in GaN$(000bar{1})$ nanowires using photoluminescence spectroscopy under both continuous-wave and pul
sed excitation. The photoluminescence intensities of these two samples quench only slightly between 10 and 300 K, which is commonly taken as evidence for high internal quantum efficiencies. However, a side-by-side comparison shows that the absolute intensity of the Ga-polar quantum wells is two orders of magnitude higher than that of the N-polar quantum disks. A similar difference is observed for the initial decay time of photoluminescence transients obtained by time-resolved measurements, indicating the presence of a highly efficient nonradiative decay channel for the quantum disks. In apparent contradiction to this conjecture, the decay of both samples is observed to slow down dramatically after the initial rapid decay. Independent of temperature, the transients approach a power law for longer decay times, reflecting that recombination occurs between individual electrons and holes with varying spatial separation. Employing a coupled system of stochastic integro-differential equations taking into account both radiative and nonradiative Shockley-Read-Hall recombination of spatially separate electrons and holes as well as their diffusion, we obtain simulated transients matching the experimentally obtained ones. The results reveal that even dominant nonradiative recombination conserves the power law decay for (In,Ga)N/GaN{0001} quantum wells and disks.
We have theoretically studied exciton states and photoluminescence spectra of strained wurtzite AlGaN/GaN quantum-well heterostructures. The electron and hole energy spectra are obtained by numerically solving the Schrodinger equation, both for a sin
gle-band Hamiltonian and for a non-symmetrical 6-band Hamiltonian. The deformation potential and spin-orbit interaction are taken into account. For increasing built-in field, generated by the piezoelectric polarization and by the spontaneous polarization, the energy of size quantization rises and the number of size quantized electron and hole levels in a quantum well decreases. The exciton energy spectrum is obtained using electron and hole wave functions and two-dimensional Coulomb wave functions as a basis. We have calculated the exciton oscillator strengths and identified the exciton states active in optical absorption. For different values of the Al content x, a quantitative interpretation, in a good agreement with experiment, is provided for (i) the red shift of the zero-phonon photoluminescence peaks for increasing the quantum-well width, (ii) the relative intensities of the zero-phonon and one-phonon photoluminescence peaks, found within the non-adiabatic approach, and (iii) the values of the photoluminescence decay time as a function of the quantum-well width.
The surface-enhanced Raman scattering in graphene deposited on AlxGa1-xN/GaN axial heterostructure nanowires was investigated. The intensity of graphene Raman spectra was found not to be correlated with aluminium content. Analysis of graphene Raman b
ands parameters, KPFM and electroreflectance showed a screening of polarization charges. Theoretical calculations showed that plasmon resonance in graphene is far beyond the Raman spectral range. This excludes the presence of an electromagnetic mechanism of SERS and therefore suggests the chemical mechanism of enhancement.
The coherent quantum effect becomes increasingly important in the heat dissipation bottleneck of semiconductor nanoelectronics with the characteristic size shrinking down to few nano-meters scale nowadays. However, the quantum mechanical model remain
s elusive for anharmonic phonon-phonon scattering in extremely small nanostructures with broken translational symmetry. It is a long-term challenging task to correctly simulate quantum heat transport including anharmonic scattering at a scale relevant to practical applications. In this article, we present a clarified theoretical formulation of anharmonic phonon non-equilibrium Green function (NEGF) formalism for both 1D and 3D nanostructures, through a diagrammatic perturbation expansion and an introduction of Fourier representation to both harmonic and anharmonic terms. A parallelized computational framework with first-principle force constants input is developed for large-scale quantum heat transport simulation. Some crucial approximations in numerical implementation are investigated to ensure the balance between numerical accuracy and efficiency. A quantitative validation is demonstrated for the anharmonic phonon NEGF formalism and computational framework by modeling cross-plane heat transport through silicon thin film. The phonon-phonon scattering is shown to be appreciable and to introduce about 20% reduction of thermal conductivity at room temperature even for a film thickness around 10 nm. The present methodology provides a robust platform for the device quantum thermal modeling, as well as the study on the transition from coherent to incoherent heat transport in nano-phononic crystals. This work thus paves the way to understand and to manipulate heat conduction via the wave nature of phonons.
We propose a mechanism of energy relaxation for carriers confined in a non-polar quantum dot surrounded by an amorphous polar environment. The carrier transitions are due to their interaction with the oscillating electric field induced by the local v
ibrations in the surrounding amorphous medium. We demonstrate that this mechanism controls energy relaxation for electrons in Si nanocrystals embedded in a SiO$_2$ matrix, where conventional mechanisms of electron-phonon interaction are not efficient.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
