Optical and thermal energy gaps in polar semiconductors
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Advanced Energy Conversion. \ol. I, p. 115. Pergamon Press. 1961. Printed in Great Britain OPT1CAL AND THERMAL ENERGY GAPS IN POLAR SEMICONDUCTORS EDWARD MILLER, KURT KOMAREKand IRVING CADOFF* ABSTRACT THE MINIMUM energy gap of a semiconductor is usually obtained from either the infrared absorption edge, or from measurement of the resistivity or Hall coefficient as a function of temperature. While in elemental semiconductors the values for the energy gap obtained by these two techniques agree fairly well, in compounds marked discrepancies may be observed, in that the optical gap is less than the thermal gap. The optically observed energy gaps of PbTe and PbSe extrapolated to 0°K are approxi- mately 0.2 eV less than those obtained from thermal measurements. The samples were sealed in evacuated Pyrex capsules during elevated temperature measurements to prevent any composition change due to the unequal vapor pressure of the two constituents. Room temperature resistivity values obtained before and after the thermal measurements were in agreement. Our experiments indicate that the difference cannot be explained by excess carrier formation at elevated temperatures due to retrograde solubility in the systems studied. Formation of defect is a more likely mechanism. * Metallurgical Engineering Department, College of Engineering, New York University. 115
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Transcript of Optical and thermal energy gaps in polar semiconductors
Advanced Energy Conversion. \ o l . I, p. 115. Pergamon Press. 1961. Printed in Great Britain
OPT1CAL AND THERMAL ENERGY GAPS IN POLAR SEMICONDUCTORS
EDWARD MILLER, KURT KOMAREK and IRVING CADOFF*
ABSTRACT
THE MINIMUM energy gap of a semiconductor is usually obtained from either the infrared absorption edge, or from measurement of the resistivity or Hall coefficient as a function of temperature. While in elemental semiconductors the values for the energy gap obtained by these two techniques agree fairly well, in compounds marked discrepancies may be observed, in that the optical gap is less than the thermal gap.
The optically observed energy gaps of PbTe and PbSe extrapolated to 0°K are approxi- mately 0.2 eV less than those obtained from thermal measurements. The samples were sealed in evacuated Pyrex capsules during elevated temperature measurements to prevent any composition change due to the unequal vapor pressure of the two constituents. Room temperature resistivity values obtained before and after the thermal measurements were in agreement. Our experiments indicate that the difference cannot be explained by excess carrier formation at elevated temperatures due to retrograde solubility in the systems studied. Formation of defect is a more likely mechanism.
* Metallurgical Engineering Department, College of Engineering, New York University. 115
