4.2.1 Device Structure and Properties

Fig. 4.8 shows the structure of a MAGFET. The printed gate length is $ 125\,\mu\mathrm{m}$, the oxide thickness is $ 60\,\mathrm{nm}$ and the device width is $ 100\,\mu\mathrm{m}$. The drain is split into two contacts with a distance of $ 10\,\mu\mathrm{m}$ from each other. If no magnetic field is applied and the bias polarization at the drains are the same, the device behaves exactly like a MOSFET. However, if a magnetic field is present ( $ {B}{\neq}0$) the carriers in the channel are deflected as a result of the Lorentz force

$\displaystyle \mathbf{F}= q\cdot {\mathbf{v}}\times \mathbf{B}$ (4.1)

where $ \mathbf{F}$ denotes the Lorentz force, $ q$ is the charge of the carriers, and $ {\mathbf{v}}$ is the carrier velocity. This charge deflection results in a perturbed balance of the current flow in the channel area and thus in different currents $ I_{\mathrm{D1}}=I/2+{\Delta}I$ and $ I_{\mathrm{D2}}=I/2-{\Delta}I$ measured in the two drains. $ {\Delta}I$ is a function of $ \mathbf{B}$ and the geometry of the device [145]. The relative sensitivity $ {S}_r$ $ [$%$ /{\mathrm{T}}]$ of a MAGFET is defined as

$\displaystyle { S}_r = \frac{{\Delta}I}{I{\cdot}{{B}}}$ (4.2)

where $ I$ denotes the total current $ I_{\mathrm{D1}}+I_{\mathrm{D2}}$. In [147] the sensitivity is obtained as a function of several geometric parameters, such as the distance of the two drains, the channel length, the width of the source contact, and the gate overlap, but also the gate and the drain voltages. Moreover, the sensitivity is dramatically increased for low temperatures [K7].

Figure 4.8: Geometry of the simulated MAGFET structure.
\psfig{file=figures/magfet/magfet_structure, width=14cm}\end{center}\vspace*{-0.4cm}

Robert Klima 2003-02-06