Light-emitting diodes

There is a growing interest in the development of devices that can efficiently convert electrical energy into light, particularly visible light. Of special interest is the possibility that such devices may be electrically and, hopefully, even physically compatible with existing electrical devices, particularly integrated circuits. Currently available semiconductor light-emitting diodes approach this ideal. For efficient electrical → optical power conversion at visible frequencies, the semiconductor bandgap must be ≳ 1.8 eV, which rules out silicon and even gallium arsenide. In this talk, the general physical guidelines developed recently for the selection of doped semiconductors that can produce efficient near-bandgap luminescence will be reviewed. In particular, attention will be given to the relative potentialities of direct and indirect gap semiconductors and the extent to which these potentialities have been realized, mainly in III-V compounds and their alloys.