(Color online) Details of the different sets of N- and Ga-polar structures grown by PAMBE.
(Color online) 5 × 5 μm2 and (inset) 500 × 500 nm2 AFM scans of the N-polar MQW structures from sets (a) A, (b) B, and (c) C.
(Color online) XRD 2-Theta/Omega scans of the (a) N- and (b) Ga-polar MQW samples from set C. The experiment corresponds to the solid line, while the simulation is marked as dashed line.
(Color online) RT photoluminescence spectra of (a) the N- and Ga-polar samples from set C, and (b) the N-polar samples from sets A, B, and C.
STEM images of the N-polar sample from set A taken (a) at low magnification along , and (b) at higher magnification along .
(Color online) (a) AFM image and (b) line profile of the surface of the N-polar sample from set A after DSE. In (b), the red arrows on the right sketch indicate the depth of the pits in the structure.
(Color online) (a) AFM, (b) reciprocal space map of the 1 1 4 reflection, (c) XRD 2-Theta/Omega scan, and (d) RT photoluminescence spectrum of the N-polar (In,Ga)N layer from set D. In (b), the misalignment of the peaks for GaN and (In,Ga)N reveals the strong relaxation of the (In,Ga)N layer. In (d), a wide peak centered at 620 nm is resolved.
(Color online) Scanning electron microscope and superimposed monochromatic CL images of the surface of the N-polar sample from set D. Granular luminescence with a trend to longer wavelengths toward the center of the hillocks is observed by setting the CL detection wavelength at (a) 550 nm, (b) 590 nm, (c) 630 nm, and (d) 670 nm.
Growth parameters of the (In,Ga)N structures and In content x in the MQW structures determined by XRD simulations. The values in parenthesis correspond to the In content estimated from the PL results as described in Ref. 10 .
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