Rigid ion model of high field transport in GaN

Abstract

Here we report on high field transport in GaN based on the rigid ion model of the electron-phonon interaction within the cellular Monte Carlo (CMC) approach. Using the rigid pseudo-ion method for the cubic zinc-blende and hexagonal wurtzite structures, the anisotropic deformation potentials are derived from the electronic structure, the atomic pseudopotential and the full phonon dispersion and eigenvectors for both acoustic and optical modes. Several different electronic structure and lattice dynamics models are compared, as well as different models for the interpolation of the atomic pseudopotentials required in the rigid pseudo-ion method. Piezoelectric as well as anisotropic polar optical phonon scattering is accounted for as well. In terms of high field transport, the peak velocity is primarily determined by deformation potential scattering described through the rigid pseudo-ion model. The calculated velocity is compared with experimental data from pulsed I-V measurements. Good agreement is found using the rigid ion model to the measured velocity-field characteristics with the inclusion of dislocation and ionized impurity scattering. The crystal orientation of the electric field is investigated, where very little difference is observed in the velocity-field characteristics. We simulate the effects of nonequilibrium hot phonons on the energy relaxation as well, using a detailed balance between emission and absorption during the simulation, and an anharmonic decay of LO phonons to acoustic phonons, as reported previously. Nonequilibrium phonons are shown to result in a significant degradation of the velocity-field characteristics for high carrier densities, such as those encountered at the AlGaN/GaN interface due to polarization effects.

Electron drift velocity in lattice-matched AlInN/AlN/GaN channel at high electric fields

“…According to the ensemble Monte Carlo ͑MC͒ simulations, the NDM appears at electric fields about 140 kV/cm, 17,18 while full-zone MC simulation shows that the NDM in GaN appears at electric fields above 180 kV/cm. 16,28 This result disagrees with the other estimations 19 and the experimental data obtained for semi-insulating undoped GaN: 20 the threshold field for the NDM is ϳ325 kV/ cm. Theoretical MC calculations incorporating a GaN full-zone band structure show that the majority of electrons do not attain sufficient energy to effect intervalley transfer until they are subjected to higher fields ͑E Ͼ 325 kV/ cm͒.…”

“…14 An onset of mobility degradation due to the increased surface roughness was obtained for AlN thicknesses larger than 5 nm in pure ultrathin AlN/GaN structures. 15 Hot-electron transport at high electric fields was investigated experimentally and/or theoretically in bulk GaN [16][17][18][19][20][21][22][23][24][25][26][27][28] and different nitride heterostructures: AlGaN/GaN, 23,29,30 AlGaN/AlN/GaN, 31 AlGaN/GaN/AlN/GaN, 32 and LM AlInN/AlN/GaN. 33 In the AlInN/AlN/GaN structure, the electron drift velocity is measured for 100 ns voltage pulses at fields up to 70 kV/cm.…”

Understanding high-field electron transport properties and strain effects of monolayer transition metal dichalcogenides

“…S9 for convergence test), meanwhile some numerical issues have to be addressed for computation efficiency. These details can be found in the Supplemental Material [38] (see, also, references [25,26,28,29,31,34,35,37,[39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] Fig. 1a shows the average velocity ⟨ ⟩ of electrons as a function of the electric field, for both unstrained and strained MX2.…”

“…The MC method is a statistical method used to yield numerical solution to the Boltzmann transport equation (BTE) [26][27][28][29][30][31][32] which includes complex band structure and scattering processes. In contrast to low-field case where analytic solutions can be derived under certain approximations, in high field, the numerical method becomes necessary due to the nonlinear terms in BTE.…”

EXTRACTION OF GATE CAPACITANCE OF HIGH-FREQUENCY AND HIGH-POWER GaN HEMTs BY MEANS OF CELLULAR MONTE CARLO SIMULATIONS

“…Details regarding the specific wurtzite GaN fullband phonon spectra and band structure can be found in [8], [9]. Charge distribution and particle tracking in the real and momentum space are performed by a particle-based dynamics kernel selfconsistently coupled with a 2D multi-grid Poisson solver [10].…”