Cross-section high-resolution TEM image of semipolar GaN/AlN quantum wells (sample C) viewed along the and zone axes.
Low-temperature (4 K) photoluminescence of semipolar (top) and polar (bottom) GaN/AlN QWs. The dashed line indicates the GaN band gap.
Photoluminescence energy calculated as a function of QW thickness and strain state for polar and semipolar QWs.
Intersubband absorption spectra for semipolar (top) and polar (bottom) GaN/AlN QWs with different well thicknesses. The spectrum labeled with a star has been obtained by photoinduced absorption measurement.
Calculated and measured ISB absorption energy versus well thickness.
Band diagram of (0001)- and -oriented GaN/AlN (3 nm/3 nm) QWs in a superlattice. Solid lines correspond to simulations assuming the superlattice strained on AlN. The conduction band in the case of the wells being strained on GaN is included as a dashed line.
(left) ISB absorbance of semipolar sample C and the corresponding Gaussian fit (dotted line). (right) ISB absorbance of polar sample B (full line), Lorentzian fitting curves (dotted lines).
Structural parameters for the GaN/AlN polar and semipolar samples. L QW and L B are the well and barrier thicknesses, respectively.
ISB peak energy with corresponding broadening for polar and semipolar samples.
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