5.4 Model parameters used for simulation

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5.4 Model Parameters used for Simulation

The parameters for the models obtained by the procedure described above are given in Table 5.2. This consistent set is used for all simulations of DHHEMTs throughout this work. Based on this simulation set up all DHHEMTs different from HEMT_ref were fitted only within uncertainties given by the applied technology well within realistic ranges. The most important fitting parameters are the activated doping concentration, the interface charge density, the recess depth, and the shape of the Tgate.

Table 5.2 Parameters used for simulation of all DHHEMT.
Schottky contact barrier height F_B	610 meV
Interface charge density	1.0*10¹²cm^-2
Relative passivation permittivity	7.0
Low field mobility GaAs	1000 cm²/Vs
Saturation velocity GaAs	0.7*10⁷cm/s
Low field mobility AlGaAs	1000 cm²/Vs
Saturation velocity AlGaAs	0.7*10⁷cm/s
HD fitting parameter b AlGaAs	0.6
Relaxation time t_w AlGaAs	0.1 ps
Low field mobility InGaAs	6000 cm²/Vs
Saturation velocity InGaAs	1.1*10⁷cm/s
HD fitting parameter b InGaAs	0.9
Relaxation time t_w InGaAs	0.17 ps
Effective tunnel length	7 nm
Coefficients of tunneling Taylor series B_i	B_1,2 = 1.0, B_i>2 = 0.0

The HEMTs described in Section 6.1 are the only devices which posses epitaxial layers fundamentally different from HEMT_ref. Therefore a different set of parameters had to be used which will be given in that Chapter.

5.5 Investigated Parameters

Next: 5.5 Investigated Parameters Up: 5 Simulation Previous: 5.3.2.2 Simulation of the Output Characteristics

Helmut Brech

1998-03-11