Simultaneous determination of the total content of boron and phosphorus in high-resistivity silicon by ir spectroscopy at low temperatures

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Abstract
The simultaneous determination of the total concentrations of B and P in silicon (ρ≳50 Ω cm) by a simple ir‐spectroscopic technique at low temperatures (≈15 K) is reported. In general, in partly compensated semiconductor crystals only the neutral centers, e.g., the difference ‖nA−nD‖ of the donors and acceptors present, contribute to the ir absorption spectrum. Through excitation with polychromatic light containing wavelengths which cause the fundamental band transition, the previoulsy ionized compensated donors or acceptors are neutralized by the mechanism of optical charge exchange and can quantitatively be observed in the absorption spectrum. The reliability of this method was checked by a comparison of the spectroscopically determined concentrations with those evaluated by four‐point‐probe measurements. A degree of compensation below 10% has been observed only for a small fraction of the samples with ρ≳50 Ω cm.