Improving the performance of the feedback charge capacitance–voltage method

Abstract

The feedback charge capacitance-voltage method (FCM) (Mego 1986 Rev. Sci. Instrum. 58 2798) is a pure time-domain technique originally used for measuring the quasi-static capacitance of semiconductor devices. The method is based on processing the output of a charge-to-voltage converter in response to a double-step (pulse) excitation of the device. Using a transient voltage processor comprising three gated integrators connected to a mixing unit, steady-state (leakage) current may be the source of severe experimental error in capacitance. First, there is a parasitic charge during the pulse that causes an error in sampling the baseline while activating the first channel for an aperture of finite duration t. Second, any uncompensated leakage present after the pulse leads to a charge increment representing what is called conduction loss in the frequency domain. Measures to be taken towards minimizing both errors are provided, based on a simultaneous action of active leakage current compensation and second-order filtering. A simple hardware solution for optimizing the dynamic range of the FCM under the leakage is provided. A non-instrumental FCM error connected with the constant dielectric loss in diamond thin films, due to the anomalous kinetics j (t) ∝ t −1 of the transient current, is analysed. The latter causes inaccuracy in assessing the instantaneous (geometrical) capacitance of diamond-based Schottky diodes. A proper gating of the charge-to-voltage converter is suggested for removal of the predicted error.

Electrochemistry of a Carbon Microfiber Adsorbed by Cobalt Nanoparticles

“…A more detailed description of the numerical corrections of the feedback capacitance data exceeds the scope of this paper, and can be find elsewhere. 15 The experiments performed with the nanoparticles adsorbed on the carbon microfiber surface were compared to the measurements performed with a bare electrode immersed in a Co 2+ solution (prepared by using a certified reference material, producer SMU Bratislava, concentration 0.999 g/L, matrix 2% HNO3), as well as in redistilled water.…”

A low-cost circuit for high-value resistive sensors varying over a wide range

“…In this way, effects due to sensor capacitance are not present. In the sensor capacitance measurement mode, an instantaneous variation is imposed on sensor voltage supply; circuit response can be related to sensor capacitance [10]. The block diagram of the proposed circuit is shown in figure 2, while the main signal behaviour is shown in figure 3.…”

Point Defects in Chemical-Vapor Deposited Diamond, High-Purity Semi-Insulating SiC, and Epitaxial GaN

“…These defects can result in efficient recombination centers or carrier traps, and detailed information about them is required for improvement of device technology. Due to the limitations of the well known capacitance-based deep level transient spectroscopy (C-DLTS) technique [3,4] with respect to insulating and semi-insulating material we have applied isothermal chargebased (Q-DLTS) method [5][6][7] with rate window scanning [6,8] for point defects studies.…”