Temperature dependent photoluminescence of lateral polarity junctions of metal organic chemical vapor deposition grown GaN

Abstract

We report on fundamental structural and optical properties of lateral polarity junctions in GaN. GaN with Ga-to N-polar junctions was grown on sapphire using an AlN buffer layer. Results from scanning electron microscopy and Raman spectroscopy measurements indicate a superior quality of the Ga-polar GaN. An extremely strong luminescence signal is observed at the inversion domain boundary (IDB). Temperature dependent micro photoluminescence measurements are used to reveal the recombination processes underlying this strong emission. At 5 K the emission mainly arises from a stripe along the inversion domain boundary with a thickness of 4-5 lm. An increase of the temperature initially leads to a narrowing to below 2 lm emission area width followed by a broadening at temperatures above 70 K. The relatively broad emission area at low temperatures is explained by a diagonal IDB. It is shown that all further changes in the emission area width are related to thermalization effects of carriers and defects attracted to the IDB. The results are successfully used to confirm a theoretical model for GaN based lateral polarity junctions. Due to the strong and pronounced emission of IDBs even at elevated temperatures, it is demonstrated that lateral polarity junctions exhibit a strong potential for future high efficiency devices. V

Nature of excitons bound to inversion domain boundaries: Origin of the 3.45-eV luminescence lines in spontaneously formed GaN nanowires on Si(111)

“…Inversion domain boundaries (IDBs) may give rise to intense PL lines in GaN films at 3.45 eV [16,19,20]. An IDB denotes a boundary between Ga-and N-polar GaN for which two different stacking sequences have been proposed by Northrup et al [21].…”

Phonon pressure coefficients and deformation potentials of wurtzite AlN determined by uniaxial pressure-dependent Raman measurements

“…For these last three Raman modes the DFT+GGA approach reaches a fair agreement in regard to the experimental valuesb with a maximal deviation of 25−37 %. A particularly good agreement between the measured and calculatedb values (DFT+GGA or LDA) is found for the E high 2 mode, which plays an important role for the stress determination as a generally non-polar Raman mode [20]. However, the corresponding |ã| value of the E high 2 mode required for the technologically relevant quantification of biaxial stress is underestimated by 26 % (GGA) or 38 % (LDA), clearly predicting a falsified Raman mode anisotropy that can be defined based on e.g.…”

“…A corresponding complete and consistent dataset for AlN is still a necessity as a large variance is evident in the PDP values reported so far [14][15][16][17][18]. Based on such fundamental PDPs, one can not only examine the strain in bulk nitride materials by non-resonant macro-Raman spectroscopy [19], but also in nanostructures by means of µRaman spectroscopy [20]. Most recently, even tipenhanced Raman spectroscopy [21] was demonstrated for nitrides facilitating strain maps based on PDPs with a lateral resolution well below the diffraction limit.…”

Electronic Biosensors Based on III-Nitride Semiconductors

“…Figure 2a illustrates the dangling bonds for Ga-and N-polar GaN. But, Ga-polar is not equivalent to having a Ga-atom on the surface; thus even in N-polar material, the last atom on the surface can be a Ga-atom (32). The density of the dangling bonds, and accordingly that of the surface states, leads to surface band bending, as illustrated in Figure 2b.…”

“…Typically all GaN surfaces are Ga-terminated (either Ga-or N-polar) (39). In addition, III-nitride surfaces are reported to be highly reactive with oxygen, carbon, and hydrogen (32). Figure 4a shows the surface molar ratios of oxygen, gallium, and nitrogen as measured with X-ray photoelectron spectroscopy (XPS) on a Ga-and N-polar surface of GaN before (left) and after HCl cleaning.…”