The role of piezoelectric fields in GaN-based quantum wells
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The role of piezoelectric elds in GaN-based quantum wells Andreas Hangleiter, Jin Seo Im, H. Kollmer, S. Heppel, J. Off and Ferdinand Scholz MRS Internet Journal of Nitride Semiconductor Research / Volume 3 / January 1998 DOI: 10.1557/S1092578300000879, Published online: 13 June 2014
Link to this article: http://journals.cambridge.org/abstract_S1092578300000879 How to cite this article: Andreas Hangleiter, Jin Seo Im, H. Kollmer, S. Heppel, J. Off and Ferdinand Scholz (1998). The role of piezoelectric elds in GaN-based quantum wells . MRS Internet Journal of Nitride Semiconductor Research, 3, pp e15 doi:10.1557/S1092578300000879 Request Permissions : Click here
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MRS
Internet Journal Nitride Semiconductor Research
The role of piezoelectric fields in GaN-based quantum wells Andreas Hangleiter 1, Jin Seo Im1, H. Kollmer1, S. Heppel1, J. Off1 and Ferdinand Scholz1 14.
Physikalisches Institut, Universität Stuttgart,
(Received Sunday, June 21, 1998; accepted Monday, August 24, 1998)
In this contribution, we focus on the consequences of the piezoelectric field, which is an inherent consequence of the commonly used wurtzite phase of GaN, on the optical properties of strained GaN-based quantum well structures. We demonstrate that both in GaN/AlGaN and in GaInN/GaN single quantum well structures, the piezoelectric field leads to a Stark-shift of the fundamental optical transitions, which can lead to luminescence emission far below the bulk bandgap. Due to the spatial separation of the electron and hole wavefunctions in such structures, the oscillator strength of these transitions may become extremely small, many orders of magnitude lower than in the fieldfree case. From specially designed structures, we can even determine the sign of the piezoelectric field and relate it to the polarity of the layers. Under high-excitation conditions, as found in a laser diode, the piezoelectric field is almost completely screened by the injected carriers. As a consequence, the stimulated emission is significantly blue-shifted compared to the photoluminescence, which has sometimes been confused with localization effects.
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Introduction
GaInN/GaN/AlGaN quantum well structures are now at the heart of GaN-based LED‘s and lasers, which are commercially available or soon to be commercialized [1] [2]. Nevertheless, the fundamental mechanisms of spontaneous and stimulated light emission are still subject to quite some debate. In particular, localization effects due to composition fluctuations and even quantum-dot-like structures due to phase separation in GaInN quantum wells have been invoked to explain some of the observations [3] [4]. Even more recently, it has been pointed out that many of the unusual optical properties of GaN-based heterostructures can be consistently explained by
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