Thin GaAs film on GaAs/Si substrate

For realizing OEIC (optoelectronics integrated circuits) on Si substrates, the GaAs-based laser diode, with a long life, is a key device. However, GaAs grown by conventional techniques on a Si substrate presents a large number of dislocations with considerable density, which prevents the long life operation of the laser. We have reported and shown that a GaAs layer with a wide dislocation-free region has been successfully grown on a GaAs/Si substrate by micro channel epitaxy (MCE). For applying an MCE layer to a laser diode, it is important to increase the W/T ratio (the ratio of width to thickness of the MCE layer). In this report, we investigated the W/T ratio dependence on the dislocation density of the GaAs/Si substrate as well as on the micro channel width. It is found that decreasing the micro channel width did not lead to an increase in the W/T ratio. However, it is found that the W/T ratio was increased clearly when the dislocation density of the GaAs/Si substrate was decreased. By the results of AFM, it is found that the number of spiral dislocations in a cluster - the step source supplying steps for MCE growth, was decreased when the dislocation density of the GaAs/Si substrate was decreased. As a result, the decrease in the number of spiral dislocations led to a decrease in the number of growth steps, and finally it resulted in an increase in the W/T ratio.