The Laboratory of Microelectronics of the University of Napoli “Federico II” is equipped with state-of-art instrumentation for DC/AC and photo-current characterization of optoelectronic devices, including conduction mechanism analysis by means of impedance spectroscopy and electrochemical techniques.
Moreover, the laboratory has advanced instrumentation for optical characterization of detectors and materials, including optical spectrum analyzer and UV-Vis-NIR high resolution spectrometer.
Here’s a list of the technical specifications of measurements that can be performed in the lab:
• low level DC current characterization
• high-sensitivity (~ fA/Hz1/2) noise characterization in the low frequency range (<100 kHz)
• time and frequency domain analysis
• impedance measurements
• automatic and programmable DC, Low frequency Noise and Impedance measurement workflow
In the following, we list the main techniques and instruments available in the lab.
Impedance Spectroscopy
Impedance Analysis is a key technology for the characterization of semiconductors, smart and new materials, organic transistors and sensors.
In IS experiments, the sample is driven with a small sinusoidal signal superimposed to a constant bias level (voltage or current) and the impedance (modulus and phase) is measured as a function of frequency. As an example, the IS analysis of a silicon PN junction is shown in the figure.
Impedance Spectroscopy – ModuLab XM MTS
The ModuLab XM MTS – Materials Test System is an impedance analyzer capable to characterize sample impedance from 10mW to 100TW, in a frequency range from 10 mHz to 1 MHz. Our system is equipped with a femtoammeter and a high-voltage supply unit to measure very high impedance material and sensors, based on ceramics, polymers, as well as solid oxide and electrolytes.
Vector Network Analyzer – E5061B
Impedance analysis at frequency higher than 1 MHz is achieved by the E5061B ENA Vector Network Analyzer (VNA). This VNA is one of a kind in this field and it has been configured to perform impedance analysis from a few Hz to 500 MHz. Also, the analyzer allows measuring critical figure of merit of amplifiers, as open loop gain, Common Mode Rejection Ratio and Power Supply Rejection Ratio.
Optoelectronics – ModuLab XM PhotoEchem
The ModuLab XM PhotoEchem is a sophisticated potentiostat/galvanostat fully integrated with NIST-calibrated light sources (LEDs and Xenon lamp) and a monochromator. It is a great instruments for the characterization of devices such as solar cells, Perovskite cells, and any kind of photosensors in the range 300 nm – 1100 nm. Frequency and time domain techniques include Intensity Modulated Photocurrent Spectroscopy, Intensity Modulated photovoltage Spectroscopy, Impedance, Photovoltage Decay, and Quantum Efficiency.
Light Source Characterization
The optical characterization of photosensors also requires the spectral and power analysis of the light source. In our lab, this is done by means of a suite of optical characterization equipment
- Ocean Insight HR-4VIS-500 high-resolution UV-VIS Spectrometer (from 200nm to 1100nm)
- Newport Advanced Optical Power Meter 2938 R
- Beam Profiler BPRO-F25
This setup is capable to characterize very low-power light source, typically used to measure the Limit-of-Detection of photosensors.
Noise Analysis
The conduction dynamics in sensors and devices based on both traditional and innovative material con be investigated by measuring the 1/f noise at very low frequency.
This noise has been interpreted and explained as due to the superposition of trapping/detrapping processes affecting the charge carriers, with a specific distribution of the characteristic times. From the analysis of the power spectral density of the current flowing in the sensor, it is then possible to determine the exact slope and the corner frequency of the 1/f trend. From there, by using models of the trapping mechanism, it is possible to measure its most relevant figure-of-merits. The noise analysis makes it possible to investigate how the environment interacts with the sensor (light, specific analytes, temperature, pH, radiation, …)
Noise Analysis – Noise Analyzer Keysight E4727B
We have upgraded our Noise Analyzer platform to the available technology: the Keysight E4727B Advanced Low-Frequency Noise Analyzer allows measuring 1/f noise from 30 mHz to 100 MHz, with a noise floor of 10-28 A2/Hz.
