Defect related radiative recombination in mono-like crystalline silicon wafers

Abstract

We report on studies of sub‐bandgap defect related photoluminescence (DRL) signals originating from radiative recombination through traps in the bandgap of cooled mono‐like silicon wafers. Spectrally resolved photoluminescence (SPL) and multivariate curve resolution (MCR) have been used in combination, to study the behaviour of sub‐bandgap photoluminescence (PL) emissions in wafers cut from different heights in a pilot‐scale mono‐like silicon ingot. No DRL signals were found in the main mono‐like body. Strong defect related sub‐bandgap emissions correlating with heavily dislocated areas, are found directly above some of the seed junctions. The DRL signal exhibits a correlation with the number of axis with small angle misalignment in the junctions of the seeds. The signal conventionally labelled D1 (0.80 eV) decreases with ingot height. A mechanism relating this signal to oxygen is proposed. The signals D3 (0.94 eV) and D4 (1.00 eV) are found to co‐occur, supporting previous studies, and similarly to the D2 (0.87 eV) signal, their strength is found to increase with ingot height. As the content of the transition metal impurities in the ingot is supposed to increase with height, this supports a reported link between the D3 and D4 signals with Fe, as well as a link between D2 and other impurities. An emission previously found in multicrystalline material and labelled D07 (0.70 eV), is found to solely exist as the only DRL signal recorded by us in parasitic crystals, growing into the main mono‐like ingot from the crucible walls. This contradicts the common notion that the D1–D4 signals are strongly related to, and always follow dislocations. Total photoluminescence spectrum (right) and distribution (left) of the PL signal with centre energy 0.70 eV emanating from the parasitic crystals growing into the bulk mono‐like Si crystal from the crucible walls.

Spectral Characteristics and Spatial Distribution of Thermal Donors in n‐Type Czochralski‐Silicon Wafers

“…Two of the signals have been named in existing literature, where the signal at 0.807 eV is referred to as the D1 signal and the weak signal at 0.925 eV is referred to as the H‐line . A weak emission at 0.903 eV has previously been studied by us and is referred to as D090 . This coincides with the deeper level recently reported by Markevich et al Further referring to this work, a shoulder at 1.01 eV associable with the corresponding shallow level is barely visible.…”

“…The previously reported D1 (0.807 eV), H (0.925 eV), and D090 (0.900 eV) emissions are not found in the spectra from the untreated samples (Figure ) . The heat treatment at 450 °C has a marked effect on these as they emerge and get stronger with heat treatment as does the P‐line complex.…”

“…The heat treatment at 450 °C has a marked effect on these as they emerge and get stronger with heat treatment as does the P‐line complex. The H‐line is reported to appear together with the P‐line, whereas the D090 signal is reported to be present in multicrystalline material . The D1 signal is reported in multicrystalline material and in intentionally deformed Cz wafers with high content of extended dislocations .…”

“…After annealing at 650 °C, the mean spectra of sample S2‐4‐650 show a complete spectral redistribution of the DRL. This eliminated the peaks at P069, P070, P072, P074, D090, and the H‐line . Instead, a wide emission band has formed between 0.66 and 0.85 eV with a peak at the P‐line.…”

“…The samples were positioned on a liquid N 2 ‐cooled sample holder with a polished aluminum surface cooled at 85–90 K. The average photon penetration depth in silicon for radiation at 808 nm at this temperature is 65 μm. The specific details regarding the technique used has been thoroughly described in previously published articles …”