Response time of Ge-doped (Al,Ga)As-GaAs double-heterostructure LED’s

The response time of the spontaneous emission of planar double-heterostructure LED’s has been measured as a function of the majority-carrier concentration in the active layer. The response time was found to decrease from a value of 15.5 ns at p0?2×1017 cm−3 to a value of 1.6 ns at p0?2×1019 cm−3. These rise times imply amplitude-modulation bandwidths for these LED’s in excess of 200 MHz. Based on the experimental values of the response time, the diffusion length of the minority carriers in the active layer of the LED can be calculated. Values of the minority-carrier diffusion length are found to range from 10.0 μm for p0?3×1017 cm−3 to 1.45 μm for p0?2×1019 cm−3.