Optical Characterisation of AlGaN Epitaxial Layers and GaN/AlGaN Quantum Wells

Abstract

We report optical characterisation of AlGaN epitaxial layers and GaN/AlGaN quantum wells, grown by metalorganic vapour phase epitaxy on sapphire substrates. A combination of emission (photoluminescence) and absorption (photoluminescence excitation) spectroscopy provides information on the nature of the electronic states and on built-in electric fields resulting from piezoelectric and spontaneous polarisation effects. These fields are found to be considerably smaller than in previously reported work on similar structures.Introduction The wide band gap alloy AlGaN has numerous potential electronic and optoelectronic applications, such as HFETs, and UV photodetectors and emitters. However, despite this, AlGaN has been considerably less well studied than the InGaN system, due in part to difficulties in performing spectroscopy in the spectral region below 350 nm. Here we describe the application of photoluminescence (PL) and photoluminescence excitation (PLE) to study AlGaN epitaxial layers and GaN/AlGaN quantum wells (QWs). This combination of emission and absorption spectroscopy allows the material quality to be assessed, provides information on the electronic states and allows the effects of the built-in piezoelectric and spontaneous polarisation induced electric fields to be studied.

III-Nitride Short Period Superlattices for Deep UV Light Emitters

“…Fourier-transform infrared optical reflectance (FTIR) [79][80][81][82], photoluminescence (PL) [83][84][85], and cathodoluminescence (CL) [41,42,86] are widely used to estimate the effective bandgaps of AlN/Ga(Al,In)N SPSLs. At room temperature, these methods are mostly qualitative, although still very useful for express control and adjustment of light-emitter properties during fabrication.…”