Apparatus for measuring minority carrier lifetime using liquid conductor
Solar power generating capacity has grown from 83 MW in 2003 to over 7,200 MW in 2012, in the U.S. alone. As the solar industry grows, there is a significant need for quality control and testing methodologies. Both testing and quality control of photovoltaics (PV) and power electronics are essential to innovation and efficient production. Accurately testing new materials and manufacturing techniques in a quick and simple way can lead to unique insights and reduced manufacturing costs and throughput times.
Minority carrier lifetime is an important material parameter in PV. Minority carrier lifetime is highly sensitive to impurities and intrinsic defects, both which affect cell efficiency. Hence, minority carrier lifetime measurement is an ideal parameter for characterization of material quality and process control. By accurately and quickly measuring minority carrier lifetimes, materials can be adjusted and manufacturing defects can be caught quickly and cost effectively.Description
NREL scientists have developed a unique apparatus and process to determine BULK-minority carrier lifetime. This development measures the minority carrier lifetime in a semiconductor wafer or thin film from the frequency dependence of the capacitance of the junction formed by the semiconductor and a liquid conductor.
This is done by contacting the surface of a semiconductor material at a first location with the first conductive liquid probe to form a Schottky junction and contacting the surface of the semiconductor material at a second location with a second contact. A forward bias is applied to the Schottky junction causing minority carrier injection in the semiconductor material. The minority carrier lifetime of the semiconductor material is determined from the inflection frequency of the total capacitance between the contacts as a function of frequency.
This in turn results in BULK lifetime measurement and is less sensitive to surface recombination velocity and treatment. The measurement can be taken without a source of light and takes only seconds to accomplish the measurement. This method could be used for any sort of semiconductor manufacturing processes.Benefits
- No light needed
- Accurate measurement of BULK minority carriers
- Electric test only
- Less expensive
- Photovoltaics Manufacturing
- Power Electronics
|Title and Abstract||
Apparatus and methods of measuring minority carrier lifetime using a liquid probe
Methods and apparatus for measuring minority carrier lifetimes using liquid probes are provided. In one embodiment, a method of measuring the minority carrier lifetime of a semiconductor material comprises: providing a semiconductor material having a surface; forming a rectifying junction at a first location on the surface by temporarily contacting the surface with a conductive liquid probe; electrically coupling a second junction to the semiconductor material at a second location, wherein the first location and the second location are physically separated; applying a forward bias to the rectifying junction causing minority carrier injection in the semiconductor material; measuring a total capacitance as a function of frequency between the rectifying junction and the second junction; determining an inflection frequency of the total capacitance; and determining a minority lifetime of the semiconductor material from the inflection frequency.
|National Renewable Energy Laboratory||04/12/2016
|Technology ID||Development Stage||Availability||Published||Last Updated|