Wide band gap, single conductivity type semiconductor light-emitting diodes (LED's) (90) feature a bias potential across the device below that required for carrier multiplication by avalanche breakdown, together with separate means for carrier introduction, such as an electron beam or a pn junction diode (91), to achieve light emission. The addition of Fabry-Perot surfaces (154, 155) converts the LED to a semiconductor laser (150). Efficiency enhancing heterostructure, including potential wells (95, 96) and staircases (92-94), may be added to the device. Arrays of such devices (172) on a substrate (171) may be scanned by an electron beam to display video information.