Minority carrier lifetime imaging of silicon wafers calibrated by quasi-steady-state photoluminescence

Abstract Reliable process control or predictions of solar cell efficiencies from minority carrier lifetimes on silicon wafers require precise lifetime measurements. For inhomogeneous material quality this implies the necessity of adequately averaged spatially resolved lifetime measurements. Materials such as, e.g. multicrystalline upgraded metallurgical grade silicon frequently feature relatively low lifetimes, high trap densities, and several material parameters (charge carrier mobilities and net dopant concentration) that are not straightforwardly predictable or measurable. As this may substantially compromise conventional lifetime measurements, we present a solely luminescence based lifetime imaging technique, which requires virtually no a priori information about material parameters. Our approach is based on a calibration of a wafer's photoluminescence image through a precise lifetime determination of a part of this wafer via quasi-steady-state photoluminescence. Carrier mobilities, net dopant concentration, and surface morphology leave the determination of lifetime virtually unaffected, the injection dependence of lifetime is properly taken into account, and lifetimes down to the timescale of a microsecond can be reliably measured.

[1]  K. Bothe,et al.  Formation rates of iron-acceptor pairs in crystalline silicon , 2005 .

[2]  Ronald A. Sinton,et al.  Quasi-steady-state photoconductance, a new method for solar cell material and device characterization , 1996, Conference Record of the Twenty Fifth IEEE Photovoltaic Specialists Conference - 1996.

[3]  D.B.M. Klaassen,et al.  A unified mobility model for device simulation—I. Model equations and concentration dependence , 1992 .

[4]  W. Warta,et al.  High‐resolution lifetime mapping using modulated free‐carrier absorption , 1995 .

[5]  K. Bothe,et al.  Photoconductance‐calibrated photoluminescence lifetime imaging of crystalline silicon , 2008 .

[6]  D. Macdonald,et al.  Light-induced boron-oxygen defect generation in compensated p-type Czochralski silicon , 2009 .

[7]  Wilhelm Warta,et al.  Diffusion lengths of silicon solar cells from luminescence images , 2007 .

[8]  G. Hahn,et al.  Time resolved photoluminescence imaging for carrier lifetime mapping of silicon wafers , 2010 .

[9]  R. J. Schwartz,et al.  Contactless nondestructive measurement of bulk and surface recombination using frequency-modulated free carrier absorption , 1992 .

[10]  Alistair B. Sproul,et al.  Dimensionless solution of the equation describing the effect of surface recombination on carrier decay in semiconductors , 1994 .

[11]  Hall measurements and grain‐size effects in polycrystalline silicon , 1980 .

[12]  D. Macdonald,et al.  Trapping of minority carriers in multicrystalline silicon , 1999 .

[13]  K. Bothe,et al.  Electronically activated boron-oxygen-related recombination centers in crystalline silicon , 2006 .

[14]  Quantitative carrier lifetime images optically measured on rough silicon wafers , 2007 .

[15]  M. Schubert,et al.  Minority carrier lifetime in silicon wafers from quasi-steady-state photoluminescence , 2010 .

[16]  W. Kwapil,et al.  Conductivity Mobility and Hall Mobility in Compensated Multicrystalline Silicon , 2010 .

[17]  Karsten Bothe,et al.  Dynamic carrier lifetime imaging of silicon wafers using an infrared-camera-based approach , 2008 .

[18]  A. Cuevas.  The paradox of compensated silicon , 2008, 2008 Conference on Optoelectronic and Microelectronic Materials and Devices.

[19]  T. Trupke.  Influence of photon reabsorption on quasi-steady-state photoluminescence measurements on crystalline silicon , 2006 .

[20]  M. Schubert,et al.  Photoluminescence imaging of silicon wafers , 2006 .

[21]  R. Brüggemann,et al.  Modulated photoluminescence studies for lifetime determination in amorphous-silicon passivated crystalline-silicon wafers , 2006 .

[22]  M. Schubert,et al.  Simultaneous determination of carrier lifetime and net dopant concentration of silicon wafers from photoluminescence , 2010, 2010 35th IEEE Photovoltaic Specialists Conference.

[23]  W. Warta,et al.  Imaging method for laterally resolved measurement of minority carrier densities and lifetimes: Measurement principle and first applications , 2003 .

[24]  Max J. Schulz,et al.  Lifetime mapping of Si wafers by an infrared camera [for solar cell production] , 2000, Conference Record of the Twenty-Eighth IEEE Photovoltaic Specialists Conference - 2000 (Cat. No.00CH37036).

[25]  Wilhelm Warta,et al.  Determination of local minority carrier diffusion lengths in crystalline silicon from luminescence images , 2009 .

[26]  R. E. Thomas,et al.  Carrier mobilities in silicon empirically related to doping and field , 1967 .

[27]  Robert Hull,et al.  Properties of Crystalline Silicon , 1999 .

[28]  W. Warta,et al.  Averaging of laterally inhomogeneous lifetimes for one-dimensional modeling of solar cells , 2003 .

[29]  R. Brendel,et al.  Sensitivity and transient response of microwave reflection measurements , 1995 .

[30]  K. Bothe,et al.  Dynamic photoluminescence lifetime imaging for the characterisation of silicon wafers , 2011 .

[31]  M. Abbott,et al.  Self-consistent calibration of photoluminescence and photoconductance lifetime measurements , 2005 .

[32]  A. Ghosh,et al.  Hall mobility of polycrystalline silicon , 1980 .

[33]  K. Bothe,et al.  Combined dynamic and steady-state infrared camera based carrier lifetime imaging of silicon wafers , 2009 .

[34]  M. Schubert,et al.  Separation of local bulk and surface recombination in crystalline silicon from luminescence reabsorption , 2010 .

[35]  M. Schubert,et al.  Spatially resolved lifetime imaging of silicon wafers by measurement of infrared emission , 2003 .

[36]  David Hinken,et al.  Determination of the effective diffusion length of silicon solar cells from photoluminescence , 2009 .