Distribution of nitrogen atoms in dilute GaAsN and InGaAsN alloys studied by scanning tunneling microscopy

Abstract

Nitrogen atoms in the cleaved (1 0) surfaces of dilute GaAsN and InGaAsN alloys have been studied using cross-sectional scanning tunneling microscopy. The distribution of nitrogen atoms in GaAs0.983N0.017 and In0.04Ga0.96As0.99N0.01 alloys is found to be in agreement with random statistics, with the exception of a small enhancement in the number of [001]-oriented nearest neighbor pairs. The effects of annealing on In0.04Ga0.96 As0.99N0.01 alloys has been studied by scanning tunneling spectroscopy. Spectra display a reduced band gap compared to GaAs but little difference is seen between as-grown versus annealed InGaAsN samples. In addition, voltage dependent imaging has been used to investigate second-plane nitrogen atoms.

Scanning tunneling microscopy contrast of isovalent impurities on the GaAs (110) surface explained with a geometrical model

“…For indium, typically, a bright contrast is observed in empty-state imaging conditions [20,[26][27][28], and for filled-state imaging at low indium concentrations there appears to be no indium contribution to the image [20]. This agrees with our simulations, which also show a bright contrast in the emptystate imaging and no indium contrast in the filled-state images.…”

“…There is also promising agreement for both N and Sb in empty-state imaging conditions. XSTM images show that N-doped GaAs [9,20] gives rise to a dark contrast on top of the N atom. Reference [20] also shows weak bright contrast for empty-state images of nitrogen, which agree qualitatively with the results of the simulation shown in Fig.…”

Spatially resolved electronic structure of an isovalent nitrogen center in GaAs

“…X-STM has been applied successfully in the past to image nitrogen atoms in GaAs as atomically sized features and determine the distribution of nitrogen in various structures such as quantum wells [45][46][47][48][49]. However, until recently little attention has focused on the imaging of the electronic state of nitrogen [50].…”

Structural properties of GaAsN∕GaAs quantum wells studied at the atomic scale by cross-sectional scanning tunneling microscopy

“…The distribution of N atoms in a metalorganic vapor phase epitaxy ͑MOVPE͒ grown GaAsN alloy with 1.7% N was studied by X-STM a few years ago. 9,10 Three different N-related features on the ͑1−10͒ surface were found and no evidence of clustering was observed. 9,10 Nevertheless, the N distribution homogeneity could depend on the amount of N in the alloy and in the growth conditions, which differ considerably between the MOVPE and molecular beam epitaxy ͑MBE͒ techniques.…”

“…8 All these have motivated a strong effort in the last years on the structural characterization of ͑In͒GaAsN alloys, but only very few of these studies were performed using cross-sectional scanning tunneling microscopy ͑X-STM͒. [9][10][11] This technique is very useful because it allows to image the cross section of a QW or bulk layer with atomic resolution and distinguish between the different atoms in the alloy. The distribution of N atoms in a metalorganic vapor phase epitaxy ͑MOVPE͒ grown GaAsN alloy with 1.7% N was studied by X-STM a few years ago.…”