Nonradiative damage measured by cathodoluminescence in etched multiple quantum well GaAs/AlGaAs quantum dots

Abstract

We report a study of nonradiative surface recombination in etched GaAs quantum well structures. Low-temperature cathodoluminescence was used to measure the relative luminescence efficiencies of etched quantum dots as a function of size, etch depth and etching conditions, and quantum well width. The relationship between etching damage and quantum well width was determined by using three samples, each consisting of three quantum wells of 2, 4, and 9 nm thickness, with the placement of the wells relative to the surface varied systematically. Arrays of quantum dots which ranged in size from 5 μm down to 40 nm were produced by electron beam lithography and reactive ion etching or ion beam assisted etching. The nonradiative surface damage produced by the etching process degrades the luminescence efficiency in quantum dots smaller than 1 μm in diameter. We have determined that etching processes which use argon gas increase the nonradiative surface layer thickness compared to etching processes which use xenon. We have also found that the lowest confinement energy quantum well is most strongly affected by the sidewall damage and the highest confinement energy quantum well is affected the least by the damage.