The Effect of Interfacial Contamination on Antiphase Domain Boundary Formation in GaAs on Si(100)

As integrated circuits continue to shrink, there is growing interest in the use of III-V compound semiconductors to increase performance at lower operating power. Some III-V semiconductors offer beneficial electrical properties over Si, but industry tools are based on large Si wafers. Thus, III-Vs will have to be integrated onto Si. A major hindrance to integration is the formation of defects such as antiphase domains in the III-V layer due to the nature of growing a polar material on a nonpolar substrate. It is well known that annealing Si(100) substrates at temperatures near 1000 °C can induce the formation of double steps on the surface which can inhibit the formation of antiphase domain boundaries (APBs). However, this process requires a large thermal budget, which may not be compatible with other existing devices on the chip. Thus, the relationship between APB behavior and process conditions must be better understood in order to realize meaningful reduction in APB density with lower thermal budgets. One major factor associated with increased defect density is the presence of interfacial impurities between the epitaxial III-V layer and Si. In this study, 450 nm thick GaAs films were grown on 300 mm Si(100) substrates (exact cut) by an Applied Materials III-V MOCVD (metal-organic chemical vapor deposition) system. The substrates were cleaned with a dry remote fluorinated plasma prior to growth. Samples were characterized using a chemical etch and scanning electron microscopy to quantify APB density, transmission electron microscopy to study the depth evolution, and secondary ion mass spectrometry to quantify the carbon and oxygen doses at the interface. It was found that for an approximately 10x range of interfacial carbon and oxygen dose, the APB density increased logarithmically from a value of 0.14 μm^-1 to a maximum of 3.2 μm^-1. This is believed to be the first quantitative correlation between carbon/oxygen contamination and APB density, of particular relevance to reduced thermal budget processing.