Microwave Volt–Impedance Spectroscopy of Semiconductors

Microwave Resonant Spectroscopy of Semiconductors with Micrometer Resolution

“…The Z−V-method developed in [32,33] is based on the measurement by using the probing station Cascade Microtech (CM) of the frequency spectrum of impedance of the probe−sample system Z( f , U) as a function of the DC voltage U applied to the probe. Electrophysical parameters of the sample are determined by solving of corresponding inverse problem.…”

“…First, let's consider conventional system of measurements implemented in [32], when the spectrum Z( f ) is determined by the spectrum of the complex coefficient of reflection S11( f ) = Ŵ( f ) (in the system of S-parameters) with direct connection of CM-probe to one of the ports of vector network analyzer. Here…”

“…To resolve the inverse problem successfully the key requirement is a high accuracy of the theoretical model. The studies [31,32] noted a beneficial circumstance: in case of the probe (antenna) of regular coaxial shape the analytical model proposed in [16] becomes accurate enough for solving at least three-parameter inverse problems. The characterization performed in the [31] for the diode structure with the resolution of 10−60 µmis an example of solving of the problem in question.…”

“…Appearance for the last 10−15 years of commercial probing stations that operate in the frequency range up to ∼ 100 GHz (such as Cascade Microtech) allows to produce a MW-spectrometer that combines locality of NFMM with measurements in a wide frequency interval within the same device. The method of volt-impedance (Z−V) spectroscopy of semiconductors proposed in [33] and proven experimentally in [32] enables obtainment of a full set of electrophysical characteristics of semi-conductor wit micron lateral resolution by solving the three-parameter inverse problem: concentration, mobility, type of free charge carriers, specific conductivity. As a result it has become possible to carry into the MW-range such informative methods of study of semiconductors as volt-farad (C−V) diagnostics [34] and the admittance spectroscopy (AS) [35][36][37].…”

“…Both methods were applied earlier at low (not more than 10 MHz) frequencies, due to which they did no provide for micron resolution. However, the possibility of obtaining additional information on the conductivity of structures with the Schottky barrier by means of the Z−V-method was implemented incompletely according to the publication [32]. The problem was insufficient accuracy of measurements of real part of impedance of the structures within the low-frequency ( f < 500 MHz) region of the spectrum.…”