# HEMT structure (High Electron Mobility Transistor)¶

Input files:
• HEMT_1D_nnpp.in

• HEMT_2D_nnpp.in

• HEMT_3D_nnpp.in

Note

If you want to obtain the input files that are used within this tutorial, please check if you can find them in the installation directory. If you cannot find them, please submit a Support Ticket.

Scope:

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

## HEMT structure¶

Input file: HEMT_1D_nnpp.in

The structure consists of the following material layers:

 width [nm] material 1 Schottky barrier 0.2 eV 2 10.0 $$In_{0.532}Ga_{0.468}As$$ 3 25.0 $$Al_{0.477}In_{0.523}As$$ 4 50.0 $$In_{0.532}Ga_{0.468}As$$ 5 300.0 $$Al_{0.477}In_{0.523}As$$ 6 300.0 InP

The conduction band edge profile without doping is plotted in Figure 2.5.2.15.

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 2.5.2.16. The electron density is plotted in blue.

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_nnpp.in, HEMT_3D_nnpp.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