Monte Carlo device simulator for III-V materials

Overview of Finite Element Ensemble Monte Carlo Device Simulator

Hight Electron Mobility Transistors (HEMTs) and Metal Semiconductor Field Effect Transistors (MESFETs) are simulated using a Monte Carlo Heterojunction 2D Final element (MC/H2F) device simulator.

Typical features of our Monte Carlo engine in the device simulator include:

implementation of the finite element mesh for accurate description of the gate and recess shapes
inclusion of the external resistances in post-processing
surface pinning
analytic non-parabolic three-valley conduction band model for electrons
scattering mechanisms in the Monte Carlo module consist electron interactions with:
1. ionized impurities (third-body exclusion)
2. neutral impurities
3. elastic acoustic phonons
4. piezoelectric deformation potential (if applicable)
5. non-polar optic phonon (intravalley and intervalley)
6. polar optic phonon (intravalley)
7. alloy scattering (if applicable)
8. impact ionization (if applicable)
strain effects on electron effective masses, material bandgaps, optical deformation poptentials, and optical phonon energies are also included in the InGaAs channel
gate tunnelling model using the thermionic approach can be included as an additional simulation process at each time step

Results for the MESFETs grown on GaAs substrate using GaAs/AlGaAs material system:

velocity overshoot effects may be engineered by a design of recess region
surface potential pinning is responsible for the reduction in the drain current

Results for pseudomorphic HEMTs (PHEMTs) grown on GaAs substrates with InGaAs channels (for more details look in papers listed in the Publications web-page):

high overshoot velocities in the channel are consistent with measured characteristics
effect of velocity overshoot on the direct current (DC) and radio frequency (RF) performance can be simulated in detail
introduction of the compressive or tensile strain into the channel allows to employ a strain engineering in PHEMTs
channel strain engineering may span a wide spectrum of low mobility values and high field overshoot characteristics
complete RF analysis using the Ramo-Shockley theorem can be compared with experimental results ( Ultrafast Systems).
complete study of the double doped design of PHEMTs
device breakdown investigations due to both impact ionization and gate tunnelling
comprehensive study of the electron ballistic transport along the channel in scaled PHEMTs

I_D-V_D characteristics obtained from the MC/H2F device simulator are calibrated against experimental data as shown in Fig. 1. after they are remapped by including external resistances.

I-V
characteristics of the 120-nm gate length <i>P</i>HEMT

Figure 1: I-V characteristic (drain current versus drain voltage) of the calibrated PHEMT with a gate length of 120~nm. Full symbols represent experimental data for several fixed gate voltages. Open symbols represent MC simulations when external resistances of the drain and source are included. The I-V characteristic for an intrinsic device (dashed line) is shown for comparison at a gate voltage of 0.4 V.