Abstract:

GaN-based heterostructures are of special interests for the fabrication of high electron mobility transistors (HEMTs) for high power, high temperature and high frequency applications. Owing to the strong spontaneous and piezoelectric polarizations in III-nitrides, the polarization-induced electric field at an AlxGa1-xN/GaN heterointerface is as high as ~ MV/cm. This leads to a significant increase of the sheet density and the narrower confinement of the two-dimensional electron gas (2DEG) in an AlxGa1-xN/GaN heterostructure in comparison with that in an AlxGa1-xAs/GaAs one. Due to the much deeper triangular quantum well and the much higher 2DEG density at AlxGa1-xN/GaN heterointerfaces, the subband structures, the transport properties of the 2DEG and other properties in AlxGa1-xN/GaN heterostructures are probably different from those in AlxGa1-xAs/GaAs ones. On the other hand, GaN-based semiconductors are the potential candidates for spintronics because of the long spin relaxation time in these materials which can persist to room temperature. Although the spin-orbit coupling parameter is thought to be small in wide band-gap semiconductors, the strong polarization-induced electric field in AlxGa1-xN/GaN heterostructures may enhance the spin-orbit interactions. Therefore, the spin properties, especially the spin-orbit interaction, of the 2DEG in GaN-based heterostructures are necessary to be further understood for their potential application in spintronics. Magneto-transport measurement is powerful to understand the transport properties of the 2DEG in semiconductor heterostructures. In this study, based on the growth of AlxGa1-xN/GaN heterostructures of high quality by means of metal organic chemical vapor deposition (MOCVD), the fine subband structures and the 2DEG occupation, the magneto-intersubband scattering (MIS) effect of the 2DEG, the effective mass of the 2DEG, and the zero-field spin splitting of the 2DEG in AlxGa1-xN/GaN heterostructures have been studied in detailed. Meanwhile, the circular photo-galvanic effect (CPGE) induced by the spin-orbit interactions of the 2DEG in AlxGa1-xN/GaN heterostructures has also been investigated.
 
 
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