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Influence of the carrier gas composition on morphology, dislocations, and microscopic luminescence properties of selectively grown GaN by hydride vapor phase epitaxyWe study radiative and nonradiative recombination at individual dislocations in GaN by cathodoluminescence performed in a transmission electron microscope. The dislocations are produced by indentation of dislocation free single crystals and have a-type Burgers vectors (b ϭ1/3͗112 0͘). They are aligned along ͗112 0͘ directions in the basal plane. Our direct correlation between structural and optical properties on a microscopic scale yields two main results: ͑i͒ 60°-basal plane dislocations show radiative recombination at 2.9 eV; ͑ii͒ screw-type basal plane dislocations act as nonradiative recombination centers. We explain the nonradiative recombination by splitting this dislocation into 30°partials that have dangling bonds in the core. The dissociation width of these dislocations is Ͻ2 nm.

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This letter reports the identification of long-range ordering in AlGaN compounds along the pyramidal planes by transmission electron microscopy. This ordering consists of the alternate stacking of GaN and AlN layers on {11̄01} planes and is evidenced by the comparison of experimental diffraction patterns along [011̄0] and [112̄0] with calculated patterns. A formation model of this ordering is presented. It is based upon Ga incorporation on reduced-N coordination sites that are located at step edges on {11̄01} pit facets.

Articles you may be interested inStrain-induced nitrogen incorporation in atomic layer epitaxy growth of InAsN/GaAs quantum wells using metal organic chemical vapor deposition Appl. Phys. Lett. 95, 051102 (2009); A comparison of photoluminescence properties of InGaAs/GaAs quantum dots with a single quantum wellWe propose a method that solves the problem of the independent determination of the indium and nitrogen concentrations in a strained quaternary InGaAsN superlattice. The method is experimentally based on the simultaneous measurement: ͑i͒ of the tetragonal lattice distortion of the unit cell from high resolution micrographs and ͑ii͒ of the intensity of the chemically sensitive ͑002͒ reflection from dark field images. As an example, we evaluate InGaAsN quantum wells with a nominal N concentration of 1.7% and with In concentrations of 10%, 20%, or 35%. We reveal local fluctuations of the In and N concentrations over distances down to 4 nm with a sensitivity of 0.1% for N and 1% for In fluctuations in this distance range.