Microwave detection of minority carriers in solar cell silicon wafers

Measurement accuracy analysis of photocarrier radiometric determination of electronic transport parameters of silicon wafers

“…1 In addition to the PTR and PCR techniques, several other methods based on pulsed or modulated photoexcitation have been developed to determine simultaneously the carrier lifetime and surface recombination velocity, notably (pulsed or modulated) free-carrier absorption (FCA) [14][15][16][17][18][19] and microwave photoconductance decay (-PCD). [20][21][22][23] In the modulated FCA or -PCD technique, the simultaneous determination of the carrier lifetime and surface recombination velocity is implemented using only the phase data, 23,24 therefore the sensitivity of the measurement and the number of parameters to be determined are limited. The sensitivity would be improved by engaging both amplitude and phase data in the multi-parameter fitting procedure, as is done in PTR or PCR measurements.…”

Contactless Microwave Measurements of Photoconductivity in Silicon Hyperdoped with Chalcogens

“…Photoinduced changes in microwave reflectivity are routinely used to measure photoconductivity without the confounding effects of electrical contacts. [11][12][13][14][15] In this technique, photocarriers generated by an optical pump beam lead to a small increase in the absorption of a microwave probe beam, which is detected as a decrease in the intensity of reflected microwaves. We report microwave reflectivity measurements of steady-state photoconductivity in silicon hyperdoped with S and Se by ion implantation followed by nanosecond pulsed laser melting.…”

“…Nevertheless, comparison with the etched sample would detect anomalous photoconductivity at 1060 nm, as might be expected from Said et al 3) Although the hyperdoped layer's resistivity of roughly 0.005 ( cm) À1 is several orders smaller than that of the substrate, the layer's thinness ensures that it will have a small effect on samples' microwave reflection and absorption in the dark. 13) Noting that the change in absorption coefficient is proportional to the change in conductivity, 15) in which C is the constant of proportionality, ÁN is the total number of photocarriers generated per second, and and are averages over z weighted by the steady-state photocarrier distribution. Normalizing by the number of incident photons arriving per second gives signal photons per second…”

Classification of silicon solar cells using Electroluminescence texture analysis

“…Electroluminescence intensity is proportional to the number of minority carriers in base layers, that is their life time and diffusion length [1]. Therefore Electroluminescence (EL) imaging techniques [2] can be employed to analyze the minority carrier diffusion length distribution in cells or modules, instead of other conventional methods as photoconductivity decay [3], the spectroscopic Laser Beam Induced Current (LBIC) [4] and Electron Beam Induced Current (EBIC) [5]. A Si-CCD camera can be used to capture the EL light emitted by a solar cell under forward bias condition and inhomogeneities in the EL intensity distribution will identify both intrinsic deficiencies, like dislocations and grain boundaries, and extrinsic (or process induced) deficiencies, like cracks, inclusions or bad electrical contacts.…”