Three-step growth of metamorphic GaAs on Si(001) by low-pressure metal organic chemical vapor deposition

Abstract

In this study, metamorphic growth of GaAs on Si(001) substrate was investigated via three-step growth in a low-pressure metal organic chemical vapor deposition reactor. Three-step growth was achieved by simply inserting an intermediate temperature GaAs layer between the low temperature GaAs nucleation layer and the high temperature GaAs epilayer. Compared with conventional two-step growth, three-step growth could further reduce surface roughness and etch pit density. By combining three-step growth with thermal-cycle annealing, the authors have grown a 1.8-μm-thick GaAs epilayer with root mean square roughness of only 1.8 and 0.73 nm in 10 × 10 μm2 and 2 × 2 μm2 scanning areas, respectively. The threading dislocation density of the 1.8-μm-thick GaAs epilayer was as low as 1.1 × 107 cm−2, as calculated directly from the double crystal x-ray diffraction ω-scan full width at half maximum of the GaAs diffraction peak. The corresponding etch pit density was only 3 × 106 cm−2.

Modified dislocation filter method: toward growth of GaAs on Si by metal organic chemical vapor deposition

“…The EPD decreased significantly compared to the sample using only the three-step growth method or the DFL, as shown in Fig. 7b, c [16,20]. Figure 8 shows the TEM images of the regions of the GaAs/Si interface and the DFL in the sample.…”

“…The measurement results of EPD and TEM indicated that the dislocation density of the GaAs/Si epilayer was reduced by the combination method of applying the DFL with three-layer QDs and the three-step growth method, and the combination of the two methods can effectively give full play to their advantages [16,18,20]. 6 Cross-sectional TEM images of two samples, a the sample with five layers QDs and three-step method growth, and b the sample with three-layer QDs and three-step method growth.…”

“…The threestep growth method is a modified two-step growth method by inserting an intermediate-temperature (IT) layer between the low-temperature (LT) layer and the hightemperature (HT) layer. It can effectively decrease the surface roughness and TD density [16] of the grown GaAs epilayers. In addition, the DFL with InAs QDs can reduce the dislocation density by bending dislocation direction with the strong strain field around the QDs.…”

“…Among them, the three-step growth method [16,17] and the dislocation filter layer (DFL) with multilayer quantum dots (QDs) [18][19][20] have obtained commendable experiment results. The threestep growth method is a modified two-step growth method by inserting an intermediate-temperature (IT) layer between the low-temperature (LT) layer and the hightemperature (HT) layer.…”

“…However, the dislocation density of GaAs/Si epilayer which only use the three-step growth method or the DFL with QDs individually does not meet the requirement for fabricating highquality devices. The three-step growth method can reduce dislocation density and improve the surface morphology in GaAs/Si epilayers [16], and such obtained GaAs/Si epilayers acting as buffer layers can enhance the crystalline quality of the QDs [22]. Moreover, the DFL with such QDs not only remains no dislocation, but also has good effectiveness of blocking dislocations.…”