Identifying threading dislocation types in ammonothermally grown bulkα-GaN by confocal Raman 3-D imaging of volumetric stress distribution

MOVPE growth of GaN on patterned 6-inch Si wafer

“…In order to account for the instrument spectral axis nonlinearity, a highly spectrally stable bulk ammonothermally grown GaN reference sample spectrum was also taken with each measurement. The reference sample spectrum was once meticulously linearized using dozens of neon atomic lines, explained in detail in this [17]. Each collected spectra was then Raman shifted together with the corresponding reference spectrum in a way that the peak of interest, the main Raman peak of GaN, E H 2 recovers its absolute position.…”

“…The cross-sections In contrast to previous reports on the circle shaped mesas, where compressive strain is maximum at the center and relaxes towards all the edges [12,16], here stresses distribute uniformly for the whole square mesa surface. However, the slight asymmetry in figure 9(e) could be caused by an unintentional artifact of accumulated instrumental errors [17], since biaxial stress distributions in figures 9(a) and (b) tend their highest values towards the bottom-right corners. From the comparison of figures 9(c) and (d) it is easy to note that the round corners seem to alleviate the stress more quickly than the sharp corners.…”

“…Confocal Raman spectroscopy is a nondestructive and sensitive optical method for quantitative characterization of stress distribution in GaN layers via observing Raman peak shifts [12,[15][16][17]. Modern Raman tools operate close to the optical diffraction limit and are capable of detecting the local stresses with lateral spatial resolution of only 0.5 μm [18].…”

“…For accurate measurements, a laser induced heating and stress should be considered due to their effect on the Raman peak shift [22]. Another major error source can be a lack of proper spectrometer calibration, often affected by the environment in real time, because it is used to linearize the spectral axis and thus correct the Raman peak shifts [17]. In order to estimate absolute stress values, both of these effects were accounted for in this work.…”

Оптическая характеризация структурных и электрических свойств нанослоев n-GaP, выращенных на проводящих подложках (001) n-GaP

“…Оптическая спектроскопия рамановского рассеяния света является одним из наиболее привлекательных ме-тодов исследования кристаллической структуры и динамики элементарных решеточных и электронных возбуждений. Исчерпывающую информацию о теоретических и экспериментальных исследованиях в этом направлении можно найти в работах [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. В спектрах рамановского рассеяния легированных полупроводников вследствие кулоновского взаимодействия могут проявляться два типа элементарных возбуждений -одночастичные и коллективные.…”