Optical Investigation of Molecular Beam Epitaxy Alxga1-Xn to Determine Material Quality

AlGaN and GaN have gained attention in the last few years for their applications in the blue and ultraviolet (UV) wavelength range. However, the majority of the attention has been directed to studying GaN rather than AlGaN. AlGaN is however of great interest militarily since it has a wide, direct band gap, which makes it suitable for various applications in the military such as plume detection and threat warning systems. Cathodoluminescence (CL), photoluminescence (PL), and optical absorption were used to characterize AlGaN samples grown by molecular beam epitaxy (MBE). These samples utilized an AlN buffer layer to match the AlGaN epilayer to the sapphire substrate. CL was run at four different beam energies (2, 5, 10, and 15 keV) with four different beam currents (1, 10, 50, and 90 or 100 ??A) on a GaN standard, the AlGaN samples, and the AlN buffer layer. PL was performed in an attempt to distinguish DAP transitions that were not observed in CL. PL was done on the GaN standard and the AlGaN samples (x = 0.10, 0.20, and 0.30).