Temperature dependence of the built-in electric field strength of AlGaN/GaN heterostructures on Si(111) substrate |
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Authors: | AT Winzer R Goldhahn G Gobsch A Dadgar H Witte A Krtschil A Krost |
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Institution: | aInstitut für Physik, Technische Universität Ilmenau, PF: 100565, 98684 Ilmenau, Germany;bInstitut für Experimentalphysik, Otto-von-Guericke Universität Magdeburg, PF: 4120, 39016 Magdeburg, Germany |
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Abstract: | Photoreflectance spectroscopy was used to measure the barrier electric field strength F of as-grown AlGaN/GaN heterostructures on Si(111) substrate with two-dimensional electron gases in the temperature range from 80 up to 295 K. The Al-contents were in the range from 12 to 20%. Despite the difference of Al-contents and the large temperature variation we find only minute changes of F. This behaviour is explained by an almost constant strain state and thus a constant piezoelectric polarisation, which was concluded from the analysis of the GaN free excitonic transitions observed by photoluminescence excitation spectroscopy. Self-consistent conduction band calculations point to a pinning of the potential of the bare surface at 0.6 V, attributed to a large density of surface donor states. |
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