Surface Photovoltage Spectrometer

The surface photovoltage method (SPV method for short) obtains the minority carrier diffusion length by measuring the surface voltage generated by light on the surface of semiconductor materials. The principle is: irradiate the surface of the semiconductor material with monochromatic light with energy greater than the bandgap width of the semiconductor material, and generate electron-hole pairs inside it. The electrons and holes diffused to the near-surface space charge region of the semiconductor material driven by the concentration gradient will be separated by the self-built electric field to form a photogenerated voltage, that is, the surface photovoltage.

The minority carrier diffusion length can be obtained according to the relationship between the surface photovoltage and the photon flux density and wavelength of the incident monochromatic light, the light absorption coefficient of the material, and the minority carrier diffusion length, and then the minority carrier lifetime can be obtained. The SPV method is the main method to characterize the minority carrier diffusion length of semiconductor materials, and its advantages are as follows.

1. A steady-state method that is independent of time, thereby avoiding the influence of in vivo and surface recombination on test results.

2. In general, the surface recombination process does not affect the test results of the minority carrier diffusion length, and the surface recombination rate only affects the surface photovoltage signal intensity, so there is no need for special treatment of the surface of the material.

3. A non-contact test method, which has low test cost, is easy to operate, is not easily disturbed, and can implement surface scanning (mapping).

Sample Requirements

Powder materials need to be ground into fine particles. Powder samples are packed in glass bottles or plastic tubes. Please do not put them in sample bags to avoid static electricity affecting sampling. The cumulative dosage volume is not less than 0.3ml.
The film material is required to have a certain thickness, and the area is preferably 20 mm × 5 mm ~ 40 mm × 15 mm, similar to the electrochemical working electrode, which needs to reserve a section of blank conductive glass.
For semiconductor and crystal testing, it is necessary to lead out the cathode and anode connectors in advance. Thin films, semiconductors, and crystals can only be tested for surface photovoltage.
For steady-state testing, please advise the scanning speed and testing range, as well as the approximate excitation wavelength.
For transient information, please advise the excitation wavelength and approximate excitation intensity.

Application

Measure surface photovoltage and photocurrent of photoelectric functional materials
Identify the conductivity type of semiconductor materials
Measure the diffusion distance and direction of carriers
Measure the bandgap width of a semiconductor