Measurements of interface potentials in quantum wells

Recently established quantitative measuremetns of electrical field profiling in semiconductor devices by scanning electron microscopy (SEM) were applied to study Al0.2Ga0.8AsGaAsIn0.2Ga0.8As interfaces. Secondary electron imaging, namely dark voltage contrast (DVC), was taken from a 200 Å In0.2Ga0.8As layer and its interfaces with adjacent regions. The measurements of electrical field profile are constituted of digital imaging of a quantum well structure with no bias and imaging of the same structure with electrical bias. The final frame, being a subtraction of two images, was calibrated due to applied biases. This method allows elimination of most surfaces features and visualization of the shape of a potential barrier in a quantum structure. Our measurements reveal that an interface potential does not follow the classical box-like shape. Measurements of the main potential steps in a biased quantum well were supported by the results of light and electron beam scanning of the same structure.