I use hf C-V and conductance method to determine the interface state density of MOS structures in terms of voltage. I am not able to show the distribution in terms of energy. How do i convert the voltages into energy?
Normally, the interface state density is expressed as the number of states per unit area of the interface per unit energy in the semiconductor band-gap. This energy is the potential energy and the potential energy of electron is simply the electron charge magnitude, e, times the potential, V, i.e. eV. So the interface trap density distribution per area per Volt (cm-2V-1) is the same as the interface trap density distribution per area per energy (cm-2eV-1).
For example in device grade silicon MOSFET, the mid-gap interface state density is of the order of 1010 cm-2eV-1.
Since the interface state capacitance density Cit is defined as Cit = qDit, where q is the electron charge magnitude, and Dit is the interface trap density, the unit of Dit has to becm-2V-1.
Normally, the interface state density is expressed as the number of states per unit area of the interface per unit energy in the semiconductor band-gap. This energy is the potential energy and the potential energy of electron is simply the electron charge magnitude, e, times the potential, V, i.e. eV. So the interface trap density distribution per area per Volt (cm-2V-1) is the same as the interface trap density distribution per area per energy (cm-2eV-1).
For example in device grade silicon MOSFET, the mid-gap interface state density is of the order of 1010 cm-2eV-1.
Since the interface state capacitance density Cit is defined as Cit = qDit, where q is the electron charge magnitude, and Dit is the interface trap density, the unit of Dit has to becm-2V-1.
You need to first find the surface potential corresponding to the bias voltage in your C-V or G-V measurement. You can numerically evaluate the Berglund integral to determine this. Otherwise, you can compare the measured C-V data to a calculated C-Surface potential curve. However, you will need to accurately know several parameters of your device including doping concentration, flatband voltage, oxide thickness, etc. Once you have mapped the bias voltage in your measurement to a surface potential, then you can simply use the energy band diagram of the MOS capacitor to determine the energy level in the bandgap. The Nicollian-Brews textbook is a good resource.
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