X-Ray Diffraction and Photoluminescence Studies of InN Grown by Plasma-Assisted Molecular Beam Epitaxy with Low Free-Carrier Concentration

Abstract

We report studies of InN grown by plasma-assisted molecular beam epitaxy. GaN templates were first grown on sapphire substrates followed by InN overgrown at 457°C to 487°C. Atomic force microscopy shows the best layers to exhibit step-flow growth mode of the InN, with a root-mean-square roughness of 0.7 nm for the 2 lm 9 2 lm scan and 1.4 nm for the 5 lm 9 5 lm scan. Measurements of the terrace edges indicate a step height of 0.28 nm. Hall measurements at room temperature give mobilities ranging from 1024 cm 2 /V s to 1904 cm 2 /V s and the electron concentrations are in the range of 5.9 9 10 17 cm -3 to 4.2 9 10 18 cm -3 . Symmetric and asymmetric reflection x-ray diffraction measurements were performed to obtain lattice constants a and c. The corresponding hydrostatic and biaxial stresses are found to range from -0.08 GPa to -0.29 GPa, and -0.05 GPa to -0.32 GPa, respectively. Low-temperature photoluminescence peak energies range from 0.67 eV to 0.70 eV, depending on residual biaxial stress, hydrostatic pressure, and electron concentrations. The electron concentration dependence of the estimated Fermi level is analyzed using KaneÕs two-band model and conduction-band renormalization effects.

Study on Neutron Irradiation-Induced Structural Defects of GaN-Based Heterostructures

“…It can be seen that the FWHMs of both samples increase after irradiation, and that of the (102) planes, it shifts more significantly. As the FWHM of the (002) (the (102)) plane corresponds to densities of screw dislocations (edge dislocations) [11,12], the densities of edge dislocations show a larger increment after the irradiation, which indicates that neutron irradiation introduces structural defects (especially edge dislocations) into GaN-based materials. In our previous neutron irradiation studies, the neutron-irradiated GaN-based heterostructures samples also exhibited much greater yellow luminescence (YL) intensities as shown in Figure 3.…”