Cathodoluminescence Studies of Quantum Dots Etched from Single Quantum Well GaAs/AlGaAs

Abstract

High resolution electron beam lithography combined with reactive ion etching has enabled the creation of GaAs structures a few tens of nanometers in lateral dimension.1 There have been several studies of luminescence from GaAs "quantum dot and wire" structures. However, reports differ as to the luminescence efficiency, peak shifts and spectral character. Photoluminescence studies of structures etched from GaAs/AlGaAs quantum well material have shown that nonradiative surface recombination typically results in no observable luminescence for quantum dots smaller than ~ 60 nm.2,3 Multiple quantum well wires have been fabricated with dimensions as small as 20 nm in cross section which still luminesce with an efficiency not degraded by the fabrication process.4 Photoluminescence measurements have indicated a spatial quantization in dots as large as 250 nm.5 Other photoluminescence measurements of various size dots show no decrease in luminescence efficiency,2 compared to unpatterned material and different spectral structure attributed to quantization effects for diameters around 60 nm.6 In contrast, Forchel et al. monitored the GaAs free exciton emission from a 4 nm thick quantum well etched into wires and observed a marked decrease in luminescence intensity with decreasing wire width.7