Stable GaAs/AlGaAs light-emitting diodes (LEDs) on Si substrates were
realized by growing device structures on undercut GaAs on Si (UCGAS) w
hich reduces both thermal stress and dislocation density. The output e
fficiency of the UCGAS LEDs was almost the same as that of homoepitaxi
al LEDs, and maintained stable operation for 3000 h. The device degrad
ation mechanism in conjunction with the residual stress and the disloc
ation density was investigated, and it was found that the stress had a
more significant eff ect on device degradation than the dislocation d
ensity. The output efficiency and the thermal properties of the LEDs a
re also analyzed. UCGAS lasers were fabricated, and both efficiency an
d threshold current equal to those of homoepitaxial lasers were obtain
ed.