HEMT

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Introduction

If we want to create fast electronic devices for high frequencies, we are getting limited by the carrier relaxation time in the semiconductor materials. This problem can be partially solved when we eliminate the scatterer elements from the material. But these centers are the dopants, so we have to somehow depart the doping from the high electron density channel. This problem is solved with the remote doping effect in high electron mobility transistors, and we are going to such a device.

Structure

The example HEMT structure is depicted in figure 1., with characteristics dopant concentrations in table 2. It is built from pure GaAs in the channel and in the contacts, and from Al$_{0.8}$Ga$_{0.2}$As in the barriers.


	\input{/var/www/dokuwiki/data/media/physicswiki/hemt/HEMTstr.tex}

Figure 1. Schematics of the HEMT


	\begin{tabular}{ll}
		Contact doping in GaAs	& 1E24 $\frac{1}{m^3}$  \\
		AlGaAs doping & 5E24 $\frac{1}{m^3}$\\
		Emmiter doping & 5E23 $\frac{1}{m^3}$
	\end{tabular}

Table 1. Parameters of the simulated HEMT

Bandstructure


	\begin{tikzpicture}
		\node[inner sep=0pt] (russell) at (0,2)
		{\includegraphics[width=\textwidth]{/var/www/dokuwiki/data/media/physicswiki/hemt/Cband.png}};
		\draw [|->] (0, -1.8) --(0, 4.3);
		%\draw [draw=white,fill=white] (0,-2) rectangle (1,-0.1);
	\end{tikzpicture}

Figure 2. Schematics of the HEMT conduction band


	\input{/var/www/dokuwiki/data/media/physicswiki/hemt/bandstr.tex}

Figure 3. Band-structure of the device in the y-axis slice

The band structure at zero bias is depicted in figure 2., and the slice in the y direction is plotted in figure 3. It shows the high electron density region due the remote doping.

Voltage characteristics


	\input{/var/www/dokuwiki/data/media/physicswiki/hemt/DSsweep.tex}

Figure 4. Drain-Source Voltage characteristics


	\input{/var/www/dokuwiki/data/media/physicswiki/hemt/GSsweep.tex}

Figure 5. Gate-Source Voltage characteristics
  • physicswiki/semiconductors/hemt/hemt.txt
  • Last modified: 2019/04/09 12:40
  • by zoltan.jehn