Abstract: In an apparatus and method for imaging a sample: a) the sample to be imaged is irradiated with pulsed electro-magnetic radiation with a plurality of frequencies in the range from 50 GHz to 84 THz; b) an area of the sample is subdivided into a two dimensional array of pixels, and radiation from each pixel is detected over a plurality of frequencies; and c) an image is generated from the radiation detected in step (b) preferably using a frequency or a selection of frequencies from the plurality of frequencies in the pulsed electro-magnetic radiation. The method can be used as a medical imaging technique and can be used to image cancer tumors.

Abstract: A semiconductor device according to the invention is characterized by comprising a stacked structure which has a plurality of layers for providing rear barrier confinement potentials, an oblique side surface intersecting edges of the plurality of layers, at least one layer overlying the oblique side such that carriers can flow in a plane parallel to the oblique side surface, and narrowing means for causing carriers to flow over the edges of the plurality of layers, only in a direction of the oblique side surface.