Special issue paper. High-radiance long-lived l.e.d.s for analogue signalling

The design and evaluation of Burrus type GaAs-GaA1As double-heterojunction l.e.d.s suitable for application in analogue optical communication systems is described. Characteristics such as radiance, response time, linearity and reliability are considered. The coupling efficiencies of the l.e.d.s to optical fibres typical of those employed in practical systems are presented. Results are given of measurements made of device linearity as a function of drive level, active layer doping and ambient temperature. Implications of these linearity measurements on the use of the l.e.d.s for analogue signalling are discussed. Data on device linearity and reliability are presented, which show (a, total harmonic distortion less than ¿50 dB (100 mA d.c., 100 mA peak to peak modulation at 5 MHz) and b, extrapolated halflives greater than 105 hours at 3 kA/cm2.