Intersubband Transitions in GaN/Al_xGa_(1-x)N Multi Quantum Wells

摘要

Intersubband transitions (ISTs) in GaN/Al_xGa_(1_x)N multiple quantum wells (MQWs) were investigated using an optical absorption technique. Several samples were grown by either Molecular Beam Epitaxy (MBE) or Metal-Organic Chemical Vapor Deposition (MOCVD) and were investigated using both normal incident and waveguide configurations. The waveguides were fabricated by dicing each sample into 2 mm wide by 5 mm long pieces with two facets polished at 45 degrees with respect to the surface such that light propagates across the sample's width. Preliminary results indicate that ISTs are observable in Si-doped and undoped GaN/Al_xGa_(1-x)N MQWs. The source of these charge carriers in the undoped samples are explained as being due to the spontaneous polarization effect which exists at the GaN/Al_xGa_(1-x)N interfaces where the GaN surface has Ga-polarity. Scanning Electron Microscopy indicates that a sample containing what appeared to be a large number of cracks and or hexagonal voids lacked the presence of TSTs.