Double-heterostructure GaAs/GaAlAs light-emitting diodes (LEDs) have been f
abricated with the emitter regions beryllium doped to 2 X 10(19) and 7 X 10
(19) cm(-3). The 7 X 10(19) cm(-3) doped emitters have an internal quantum
efficiency of 10% and an optical modulation bandwidth of 1.7 GHz. The stead
y-state optical output power versus the input current shows an external eff
iciency of 2.5 mu W/mA. The 2 X 10(19) cm(-3) emitters have internal quantu
m efficiencies as high as 80%, but a reduced cutoff frequency. The external
quantum efficiency reaches 10 mu W/mA. These high-speed LEDs are produced
by reducing the radiative lifetime to 100-250 ps without significantly degr
ading internal quantum efficiency. The current results on heavily beryllium
-doped LEDs exhibit, to the best of our knowledge, the highest external eff
iciencies to date for such high doping and efficiencies close to that obser
ved for lower-doped LEDs. (C) 1999 American Institute of Physics. [S0003-69
51(99)03621-9].