Review of polarity determination and control of GaN
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Review of polarity determination and control of GaN M. Sumiya and S. Fuke MRS Internet Journal of Nitride Semiconductor Research / Volume 9 / January 2004 DOI: 10.1557/S1092578300000363, Published online: 13 June 2014
Link to this article: http://journals.cambridge.org/abstract_S1092578300000363 How to cite this article: M. Sumiya and S. Fuke (2004). Review of polarity determination and control of GaN . MRS Internet Journal of Nitride Semiconductor Research, 9, pp e1 doi:10.1557/ S1092578300000363 Request Permissions : Click here
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MRS
Internet Journal Nitride Semiconductor Research
Review of polarity determination and control of GaN M. Sumiya12 and S. Fuke1 1Shizuoka
Univeristy,
2CREST-JST,
(Received Friday, November 21, 2003; accepted Monday, February 9, 2004)
Polarity issues affecting III-V nitride semiconductors are reviewed with respect to their determination and control. A set of conditions crucial to the polarity control of GaN is provided for each of the following growth techniques; molecular beam epitaxy (MBE), pulsed laser deposition (PLD) and hydride vapor phase epitaxy (HVPE). Although GaN films might have been deposited by identical growth methods using the same buffer layer technologies, there is often a conflict between the resulting polarities achieved by different research groups. In this paper, we present the implications of the conditions used in each of the processes used for two-step metalorganic chemical vapor deposition (MOCVD), demonstrating systematic control of the polarity of GaN films on sapphire substrates. The potential for confusion in polarity control will be explained, taking into account the implications clarified in our studies. The correlation between the polarity and the growth conditions will be discussed in order to provide a mechanism for the determination and control of the crystal polarity during the growth of GaN films.
1
Introduction
The polarity of III-V nitride semiconductors is a critical issue that has hindered improvements in nitride materials and the performance of devices. The quality of the wurtzite GaN films shown in Figure 1 can be varied by the polarity, because both the incorporation of impurities and the formation of defects are related to the growth mechanism, which in turn depends on the polarity of the surface. The occurrence of a two dimensional electron gas (2DEG) and the optical properties of hetero-structures of nitride-based materials are influenced by the internal field effects caused by spontaneous and piezo-electric polarizations. Devices in all of the III-V nitrides are fabricated on polar {0001} surfaces. Consequently, their characteristics depend on whether the GaN films exhibit Ga- (+c) or N - (-c) face polarity. Therefore, it is very important to be able to determine and control the
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