Optical microscope imaging of semiconductor quantum wells

The diffusion-limited wet-etching technique is used to produce a vertical taper through an InGaAs/GaAs multiple-quantum-well (QW) heterostructure. The lateral extension of a QW layer becomes as large as a few micrometres upon being truncated at an angle below 0.1 degrees, resulting in an effective magnification factor greater than 500. This allows not just imaging of QWs but also quantitative measurements of individual QW thickness using an ordinary optical microscope. Also presented are cathodoluminescence data for the taper-etched sample, confirming that the lines appearing in the optical microscope image are indeed QWs.