Modeling of elastic, piezoelectric and optical properties of vertically correlated GaN/AIN quantum dots
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E11.14.1
Modeling of elastic, piezoelectric and optical properties of vertically correlated GaN/AlN quantum dots Sławomir P. Łepkowski1,3, Grzegorz Jurczak2, Paweł Dłużewski2 and Tadeusz Suski1 1
Unipress, Institute of High Pressure Physics, Polish Academy of Sciences, ul. Sokołowska 29, 01-142 Warszawa, Poland 2 Institute of Fundamental Technological Research, ul. Świętokrzyska 21, 00-049 Warszawa, Poland 3 Faculty of Mathematics and Sciences, Cardinal Stefan Wyszyński University, Dewajtis 5, 01815 Poland ABSTRACT We theoretically investigate elastic, piezoelectric and optical properties of wurtzite GaN/AlN quantum dots, having hexagonal pyramid-shape, stacked in a multilayer. We show that the strain existing in quantum dots and barriers depends significantly on the distance between the dots i.e. on the width of AlN barriers. For typical QDs, having the base diameter of 19.5nm, the drop of the electrostatic potential in the quantum dot region slightly decreases with decreasing of the barrier width. This decrease is however much smaller for QDs than for superlattice of GaN/AlGaN quantum wells, with thickness similar to the height of QDs. Consequently, the band-to-band transition energies in the vertically correlated GaN/AlN QDs show unexpected, rather weak dependence on the width of AlN barriers. Increasing the QD base diameter leads to stronger decreasing dependence of the band-to-band transition energies vs. the width of AlN barriers, similar to that observed for superlattieces of QWs . INTRODUCTION For the last few years, nitride quantum dots (QDs) have attracted considerable attention due to their promising applications. On the one hand, in short-wavelenght optoelectronics, selforganized GaN/AlN or InGaN/GaN QDs are considered as new candidates for the active region in blue or UV light emitters [1]. One expects that the three dimensional carrier confinement present in nitride QDs can increase the optical material gain and decrease the non-radiative recombination in comparison with conventionally used nitride quantum wells. On the other hand, strong built-in electric fields present in nitride QDs, due to spontaneous and piezoelectric polarizations, make these structures attractive for quantum information processing or spintronics [2,3]. This is mainly due to strong and intrinsic exciton-exciton coupling possible in these structures. Both mentioned fields of potential applications of nitride QDs are connected with vertical stacking of QDs in the multilayer. Recently, there have been a few reports on successful growth of vertically correlated wurtzite GaN/AlN QDs stacked in multilayers [4-6]. The strong vertical ordering, along the (0001) direction, observed in the multilayers of wurtzite GaN/AlN QDs is attributed to a local lattice distortion enhancement localized directly above the previously buried QD [7].
E11.14.2
Theoretical study of optical properties of wurtzite GaN/AlN QDs have already been performed by several groups. In Ref. [8], a semi-analytic approach based on the plane wave expansion method was u
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