Abstract
In 4H silicon carbide, aluminum implantation causes unusual high compensation ratios as obtained from Hall effect investigations by fitting the neutrality equation with a single acceptor. We show that this approach cannot fully describe the experimental data, in particular in case of moderate doping and at high measurement temperatures above 450 K. We develop two extended models by adding an additional acceptor- or donor-like defect to the equation. Both approaches describe the data well. However, it turns out that an additional aluminum-correlated acceptor is the more reasonable choice. In this case, the compensation ratio stays almost independent of the implantation dose between 30 % and 40 %. The deep acceptor is located at EV + (280–400) meV.
Highlights
The exact knowledge of the net charge in doped regions of power devices is of utmost importance to achieve the desired functionality
It has been shown that especially in aluminum (Al) implanted 4H-silicon carbide (SiC) layers a high charge compensation caused by defects reduces the free hole density
We investigate various samples with Al concentrations typically used for pwell channel regions of MOSFETs and for the pillar structures in super-junction devices by Hall effect
Summary
The exact knowledge of the net charge in doped regions of power devices is of utmost importance to achieve the desired functionality. In super-junction devices, for instance, the charge balance between n- and p-doped regions predominantly determines the breakdown voltage.. It has been shown that especially in aluminum (Al) implanted 4H-SiC layers a high charge compensation caused by defects reduces the free hole density.. We investigate various samples with Al concentrations typically used for pwell channel regions of MOSFETs and for the pillar structures in super-junction devices by Hall effect. It turns out that the neutrality equation including a single acceptor level does not describe the measured free hole density. We present and discuss extended models including the temperature-dependent Hall scattering factor, excited acceptor states and additional defects. This approach allows for a reliable determination of the charge carrier compensation
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