Near-field optical characterization of GaN and InxGa1−xN/GaN heterostructures grown on freestanding GaN substrates

The influence of V defects on luminescence properties of AlInGaN quaternary alloys

“…A LT GaN buffer layer was first grown to a thickness of 35 nm at 550 • C and then a 2 µm thick undoped GaN layer was deposited at 1050 • C. This was followed by the growth of 150 nm thick quaternary layers at 850 • C. The NSOM system is implemented for ultraviolet-visible imaging and spectrally resolved emission has been detected by using a photomultiplier tube. The details of the set-up are described elsewhere [20]. The surface morphology of the layers was also studied with a Digital Instruments Nanoscope III AFM set-up operating in the tapping mode.…”

Homoepitaxy on GaN substrate with various treatments by metalorganic vapor phase epitaxy

“…Moreover, the NBE of all samples was blue-shifted after MOVPE overgrowth. Chua et al [23] indicated the blue-shifted of NBE is related to the significantly higher carrier concentration in GaN substrate compared to the overgrown epilayer. Based on the decrease in the FWHM of the NBE, the decrease in the carrier concentration in the MOVPE overgrown epilayer was determined to be due to V N .…”

Near-field scanning optical microscopic transient lens for carrier dynamics study in InGaN∕GaN

“…The spatial inhomogeneity of NSOM-PL is well known and interpreted to be the inhomogeneity of indium composition by the phase separation. [3][4][5][6][7][8][9][10][11][12][13][14][15][16] The bright regions correspond to the high density region of the carrier localization centers, which act as the radiative recombination centers ͑RCs͒. On the other hand, the spatial inhomogeneity of NSOM-TL should denote the carrier distribution in the InGaN active layer because we already knew that the NSOM-TL signal is attributed to only the ␦N ͓Fig.…”

“…1,2 In order to improve the efficiency of light emission from InGaN QW, we have to elucidate and understand the carrier dynamics and light emission mechanics. There are a lot of reports on the spatial resolved studies for InGaN by cathodoluminescence, [3][4][5] near-field scanning optical microscopy ͑NSOM͒, [6][7][8][9][10][11][12] or scanning confocal microscopy. 13,14 By these techniques, the radiative carrier recombination process has been observed with submicrometer scale.…”