HEMT structure (High Electron Mobility Transistor)

Input files:

• HEMT_1D_nnp.in

• HEMT_2D_nnp.in

• HEMT_3D_nnp.in

Scope:

This tutorial demonstrates how High Electron Mobility Transistors can be modelled with nextnano++.

HEMT structure

Input file: HEMT_1D_nnp.in

The structure consists of the following material layers:

	width [nm]	material
1		Schottky barrier 0.2 eV
2	10.0	$I{n}_{0.532}G{a}_{0.468}As$
3	25.0	$A{l}_{0.477}I{n}_{0.523}As$
4	50.0	$I{n}_{0.532}G{a}_{0.468}As$
5	300.0	$A{l}_{0.477}I{n}_{0.523}As$
6	300.0	InP

The conduction band edge profile without doping is plotted in Figure 2.4.453.

Figure 2.4.453 Calculated conduction band edge profile.

Now we add at x = 35 nm a silicon delta doping of 4.5 $\cdot$ 10¹² cm^-2 which leads to band bending. Instead of choosing a delta doping we specify a constant doping of 1.5 $\cdot$ 10²⁰ cm^-3 that extends over 0.3 nm. (1.5 $\cdot$ 10²⁰ cm^-3 $\cdot$ 3 $\cdot$ 10^-8 cm = 4.5 $\cdot$ 10¹² cm^-2)

We obtain two eigenstates and their corresponding wave functions inside the HEMT channel which leads to a two-dimensional electron gas (2DEG), see Figure 2.4.454. The electron density is plotted in blue.

Figure 2.4.454 Calculated conduction band edge profile and probability densities.

In the file bias_00000/total_charges.txt we can find the integrated electron and hole densities. The total integrated density (from 10 nm to 100 nm) which can be measured experimentally is 1.87 $\cdot$ 10¹² cm^-2 in agreement with the experiment. Most of the density is located between 45 nm and 95 nm.

2D/ 3D simulations

Input files: HEMT_2D_nnp.in, HEMT_3D_nnp.in

Input files for the same HEMT structure as in 1D, this time for a 2D and 3D simulations, are also available.

• 2D: rectangle of dimension 250 nm x 10 nm

• 3D: cuboid of dimension 250 nm x 10 nm x 10 nm

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Last update: nn/nn/nnnn