The dependence of the optical quality, i.e. the line width and homogeneity of (1 1 0) oriented quantum wells on the substrate temperature, the As pressure as well as on the AsImage species is studied by means of micro-photoluminescence. Molecular beam epitaxial growth using the AsImage dimer leads to a photoluminescence line width as narrow as 5.5 meV for 7 nm wide quantum wells compared to a value of 8 meV for the AsImage tetramer source. In addition to the small line widths which can be achieved using AsImage , quantum wells grown under these conditions are also superior to those using AsImage in terms of uniformity on a Image m length scale. In contrast, the peak mobility of a two-dimensional electron system located at a (1 1 0) oriented GaAs/AlGaAs heterointerface of Image cmImage V s is obtained for tetramer growth, while the use of AsImage degrades the electron mobility to values below 500 000 cmImage V s.