Time-domain and lock-in rate-window photocarrier radiometric measurements of recombination processes in silicon

Abstract

Time-domain and lock-in rate-window photocarrier radiometry ͑PCR͒ configurations are introduced both experimentally and theoretically to investigate the responses of p-and n-type Si wafers under a repetition-period-scanned square-wave-modulated super-band-gap laser beam which produces free excess photocarriers. The complete asymmetric time-domain carrier diffusion and recombination boundary-value problem with different front-and back-surface recombination velocities was solved in terms of the full spectrum of spatial eigenmodes and used to fit the time-domain data. The accurate measurement of the photocarrier transport properties ͑bulk lifetime, surface recombination velocities, and ambipolar diffusivity͒ was found to require the linear superposition of all the effective decay lifetimes associated with the eigenmode spectrum. The effects of the infinite prior pulse train to the current photocarrier radiometric response wave form were quantified and were found to be very important for certain ranges of transport parameters, pulse durations, and repetition periods. The time-domain formalism was further used to develop a theory for lock-in rate-window photocarrier radiometry. The application of the theory to the experimental results shows that they retain the time-domain character of the photocarrier generation and recombination processes, with data quality and signal-to-noise ratio superior to coaddition-averaged transients, especially in the case of samples exhibiting very low time-domain PCR signals.

Competition between Charge-Transfer Exciton Dissociation and Direct Photocarrier Generation in Molecular Donor-Acceptor Compounds

“…This consideration is consistent with the Onsager-type photonenergy dependence of the IPCE spectrum. Above 1.3 eV, free electrons and holes should be directly generated by photoexcitation in a manner similar to that in inorganic semiconductors; the diffusion length in Si is reported to be a few hundreds of micrometers [24][25][26]. These features can be ascribed to the inherent characteristics of CT excitons, which can be dissociated by a small excess photon energy.…”

Three-dimensional transient model for time-domain free-carrier absorption measurement of excess carriers in silicon wafers

“…On the other hand, the measured carrier lifetime values for all samples were within 10.9-27.7 ls, typical values for Si wafers. 6,15,22 The experimental results show the lifetime (10.9-27.7 ls), diffusion coefficient (10.8-26.7 cm 2 /s), and front surface recombination velocity (1.94-21.1 m/s) can be extracted precisely by the three-dimensional transient time-domain MFCA. The simulation results also indicated that a wider range of transport parameters can also be determined by the transient MFCA technique.…”

“…Then we substitute Eq. (11) into its boundary condition (9) and decompose the eigenvalue equation into two linearly independent transcendental equations 15 in the form of two sets…”

“…Luke and Cheng 14 developed a single-pulse transient model to describe photo-generated excess carriers. Later, Mandelis et al 15 presented an infinite-pulse modulated time-domain theory for photo-carrier radiometry (PCR). However, these models were only one-dimensional, which described the transport dynamics of the photo-generated carriers only in the depth direction.…”

Monitoring of amorfization of the oxygen implanted layers in silicon wafers using photothermal radiometry and modulated free carrier absorption methods

“…Measurement methods based on plasma waves are very attractive for monitoring electrical transport parameters (carrier diffusivity, lifetime of carriers and surface recombination velocities of carriers) in the ion implantated layer as well as in the substrate. Plasma waves can be detected by the measurement of the periodical component of the intensity of the IR radiation of the samples, in a PTR method, or by the measurement of the intensity of the periodical component of the transmitted probing IR beam of light in a MFCA method, or by the periodical photoluminescence in a photocarrier radiometry (PCR) method [1][2][3]. Analysis of the frequency characteristics enables determination of the recombination parameters of semiconductors with the PTR method [4,5] and the MFCA method [6][7][8][9][10][11][12].…”