Frequency-resolved microwave reflection photoconductance

Romanowski, Andrzej; Karoui, A.; Rozgonyi, G. A.

doi:10.1063/1.367946

Cited by 4 publications

(5 citation statements)

References 12 publications

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“…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.…”

Section: Introductionmentioning

confidence: 99%

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

Shaughnessy

Mandelis

2004

Journal of Applied Physics

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Simulations are performed to investigate the accuracy of the simultaneous determination of the electronic transport properties (the carrier lifetime, the carrier diffusion coefficient, and the front and rear surface recombination velocities) of silicon wafers by means of the photocarrier radiometry (PCR) technique through fitting frequency-scan data to a rigorous model via a multi-parameter fitting process. The uncertainties of the fitted parameter values are analyzed by calculating the dependence of the square variance including both amplitude and phase variances on the electronic transport properties. Simulation results show that the ability of the PCR to accurately determine carrier lifetimes gradually decreases for lifetimes longer than roughly 100 microseconds. In case the carrier diffusion coefficient is previously known, the carrier lifetime and front surface recombination velocity can be determined with uncertainties approximately ±20% or less. Experiments with an ion-implanted silicon wafer were performed and the carrier lifetime and front surface recombination velocity were determined with estimated uncertainties approximately ±30% and ±15%, respectively.

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Section: Introductionmentioning

confidence: 99%

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

Shaughnessy

Mandelis

2004

Journal of Applied Physics

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“…In this work, we assume (i) non-steady state condition at recombination center (R n ≠ R p ) and (ii) low excess carrier concentration. The second assumption allows linear equations to be used (2) by introduce the following relations 5,16 :…”

Section: Theory and Evaluation Proceduresmentioning

confidence: 99%

“…, can be described by a single Lorentzian 16,21 , peaked at the frequency f 0 , and having a maximum value, Y 0 . The Lorentzian function is plotted for four temperatures (24, 80, 180 and 240°C) in Fig.…”

Section: Theory and Evaluation Proceduresmentioning

confidence: 99%

“…The wafer sets were intentionally contaminated with Fe and Ni to a concentration of ~ 10 11 and 10 12 cm -3 , respectively. The measurement system set-up was described in our previous papers 14,16 . Figure 4 shows the measured quadrature spectra for wafers containing iron with concentrations of 5x10 11 cm -3 and 5x10 12 cm -3 , respectively.…”

Section: Measurement and Semiconductor Evaluationmentioning

confidence: 99%

“…In our study the recombination process is described by E r , N r , σ n and σ p , and their impact on the microwave reflection coefficient is investigated for different temperatures. The influence of surface recombination velocity on microwave reflection coefficient were analyzed in our previous works 14,15,16 , where both in-phase and quadrature components of the microwave reflection coefficient were presented in a complex plane as Nyquist plots. It was shown that the Nyquist plot reduces to one arc for single level recombination process and two arcs in the case of trapping-recombination processes.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of and Ti Gettering for PV Substrates: Final Subcontract Report; 28 January 1998 - 28 August 2001

Rozgonyi¹,

Karoui²,

Romanowski³

et al. 2002

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The initial project objectives were twofold; namely, to determine the optical and gettering properties of titanium and titanium oxy-nitride films, and to examine the influence of carrier recombination processes on the microwave reflection coefficient in the frequency domain such that PV materials parameters could be evaluated non-destructively. A third topic was added as the main focus of our six month contract extension, wherein we carried out a detailed characterization study of dislocated, high purity, float zone crystals grown at NREL by Ted Cizsek. These were compared with nitrogen doped CZ wafers. The accompanying report has a chapter devoted to each of these topics presented in reverse order of the above list. Highlights of these chapters include the following . With regard to dislocated FZ material we note that the average carrier lifetimes of 50 to 100 microseconds in heavily dislocated areas are still quite high for PV applications. This is attributed to the fact that the dislocations are "clean" in this high purity FZ crystal and relatively inactive electrically. This relatively low impact of a high density of dislocations on minority carrier recombination lifetime leads us to believe that the proper tailoring of SiO 2 precipitation phenomena will enable long diffusion length PV wafers to be produced which also exhibit enhanced mechanical yield behavior. Thus, the above ongoing electrical/structural approach is being extended to low oxygen content CZ wafers, as well as FZ wafers with deliberately added concentrations of oxygen. In addition, a processing bonus related to a near surface defect band induced surface texture in nitrogen doped CZ wafers is likely to have a positive impact on single crystal PV devices by simultaneously providing surface texturing and a near surface gettering sink for bulk impurities.The microwave photoconductance method was a relation for the microwave reflection coefficient in the frequency domain was found. A single level Shockley-Read-Hall nonstationary recombination model was used for the description of the carrier kinetics. Although six parameters, i.e., surface recombination velocity v s , diffusivity D n , activation energy E r , electron/hole capture cross sections σ n , σ p , and concentration N r were analyzed, only four are robust; namely v s , E r , N r c n and σ p /σ n , and among them two, E r and σ p /σ n , can be used as material parameters. These two parameters were evaluated from the frequency resolved spectra for silicon wafers intentionally contaminated with Ni and Fe. The E r and σ p /σ n values obtained for Fe, and Fe+Ni contaminated wafers were equivalent, while in the presence of Ni, the above parameters were different, indicating that these parameters can be used for material characterizationThe titanium thin film study revealed that a TiN x O y film exhibits the best optical quality; however, poor interface formation between the film and surface due to strong Ti and O bonds eliminates that film as a good external getter. Both Ti and TiN x films have ...

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Direct imaging of photoconductivity of solar cells by using a near-field scanning microwave microprobe

Hovsepyan

Babajanyan

Sargsyan

et al. 2009

Journal of Applied Physics

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A near-field scanning microwave microprobe (NSMM) technique has been used to investigate the photovoltaic effect in solar cells. As the photoconductivity of the n-type silicon layer in the solar cells was varied due to the incident light intensities and the wavelength, we could directly observe the photoconductivity changes inside the solar cells by measuring the change of reflection coefficient S11 of the NSMM at an operating frequency near 4.1 GHz. We also directly imaged the photoconductivity changes by NSMM. Photoconductivity in solar cells is determined from the visualized microwave reflection coefficient changes at the interfaces with high sensitivity.

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Frequency-resolved microwave reflection photoconductance

Cited by 4 publications

References 12 publications

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

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

Characterization of and Ti Gettering for PV Substrates: Final Subcontract Report; 28 January 1998 - 28 August 2001

Direct imaging of photoconductivity of solar cells by using a near-field scanning microwave microprobe

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