“…As spatial resolution is not always required for purely spectroscopic applications, we have developed a device based version of BEES, where ballistic electrons are provided by a metal-insulator-metal ͑MIM͒ tunneling junction. 12 In the literature there are several reports on BEES using devices, such as hot electron transistors on the basis of GaAs-AlGaAs heterostructures ͑''THETA'' devices 13 ͒ or the injector structures introduced by Rauch et al 14 However, all these experiments were carried out on highly specialized molecular beam epitaxy ͑MBE͒ grown structures and, in addition, required an advanced sample processing. In contrast to that, our MIM ͑Al-Al 2 O 3 -Al͒ injector can be used on any substrate material, provided the quality of the Schottky contact between the aluminum base layer and the semiconductor is good enough.…”