Degradation of GaAs Lasers and LEDs on Si Substrates.

The degradation of single-quantum-well graded-refractive-index GaAs lasers and LEDs grown on Si substrates by metalorganic vapor deposition was studied. The mechanism resulting in degradation appears to be identical with that observed in GaAs devices on GaAs substrates. However, the devices degrade very rapidly, even under pulsed operation, due to the presence of a very high density of nonradiative regions resulting from the dislocations caused by the 4.1 percent lattice mismatch between the GaAs and the Si substrate. Continuous operation has been obtained up to 160K. At higher temperatures the dark regions quench the emission 3-5microsecond after the start of a current pulse. This prevents the continuous operation at room temperature of these lasers. The dark regions grow rapidly in size during operation by nonradiative electron-hole recombination in the presence of the large tensile stress in the epilayer. We estimate that it will be necessary to reduce the defect density to less than ~ 10 sup 4 cm sup (-2) and prevent the growth of defects in the active layer in order to achieve reliable operation of light emitting devices.