Abstract: A semiconductor device having a hetero-junction (3) between a semiconductor layer (2A,B) having a larger band gap and a semiconductor layer (1) having a smaller band gap, in which a bidimensional charge carrier gas (4) is formed, which is limited to a mesa-shaped part (5) of the layer structure. According to the invention, the sidewall (6) of the mesa extends to within the semiconductor layer (2) having the larger band gap, but does not extend as far as the semiconductor layer (1) having the smaller band gap in order to avoid surface traps at the edge of the mesa. Application inter alia is in HEMT devices and ballistic transistors.

Abstract: A device for producing or amplifying coherent radiation includes a semiconductor device such as a laser. By means of electrons of high energy produced by a semiconductor cathode of the device, population inversion is obtained in an active layer of the laser structure. In this manner, laser action is obtained, which offers advantages, especially with II-VI materials which emit radiation of a wavelength shorter than the usual III-V materials, and which do not permit the desired population inversion to be obtained in the same manner as in III-V materials, by means of current injection across a pn junction. The semiconductor cathode and the laser structure can be arranged in mutual separation in a vacuum tube or be realized in one semiconductor body. The short-wave laser is especially advantageous for CD,DOR and VLP applications.