Suppression Of Antiphase Domains Of Epitaxial Ⅲ-Ⅴ Materials On On-Axis Si(001)Substrates

With the advent of the big data era and the rapid development of network technology,the traditional electrical interconnection cannot support such a huge amount of data traffic now.And silicon-based optoelectronic integration based on optical interconnection technology can solve this problem.Silicon optoelectronic integration has attracted more attention due to low cost and high reliability.While commercial silicon-based chips with bonding technology are complex and costly to fabricate,the technology of directly epitaxial Ⅲ-Ⅴ materials on silicon can significantly reduce fabrication costs and enable mass production.Therefore,in recent years,researchers have focused on growing high-quality Ⅲ-Ⅴ materials on Si substrates by direct epitaxy.The differences between Ⅲ-Ⅴ materials and Si crystals in lattice constant and polarity can seriously affect the quality of silicon-based Ⅲ-Ⅴ materials.In particular,planar defects called antiphase domain occur when growing polar Ⅲ-Ⅴ materials on nonpolar Si substrates with single layer atomic steps.Early researchers used Si(001)substrates with a miscut angle of 2-6° and a miscut direction of[110]to suppress antiphase domain.Researchers started to use on-axis Si substrates due to the incompatibility with standard CMOS processes.It was found that high-temperature hydrogenation annealing of onaxis Si substrates enables the transition from single layer atomic steps to double layer atomic steps on on-axis Si(001)surfaces.In general,the MBE technique does not provide a hydrogen annealing environment,but the MBE system can provide an environment such as aluminium(Al)beam flow.If the ability of Al atoms to adjust the surface phase of Si substrates can be demonstrated,the conversion of single atomic steps on the surface of on-axis Si(001)substrates into double atomic steps in the MBE system is also possible.In addition,it was found that the growth of buffer layers such as Si and AlGaAs can lead to the annihilation of antiphase domains in the Ⅲ-Ⅴmaterials.However,the mechanism behind the annihilation of antiphase domains remains unclear.Moreover,if the annihilation mechanism of antiphase domains can be explained,the experimental process can be optimized,facilitating the research process of all-MBE grown silicon-based lasers.This study performs theoretical analysis and experimental investigation to verify the problem of antiphase domains in III-V epitaxial materials on on-axis Si(001)substrate.First the antiphase domain formation energy in GaAs is calculated using first principle,and the thermodynamic stability of antiphase domains in different propagation surfaces is obtained.Subsequently,the theoretical results are compared and verified experimentally,and a reasonable annihilation mechanism for antiphase domains is presented.In addition,the adjustment of Al atoms on Si(001)surface phase is investigated,which provides a theoretical basis for the growth of GaAs/Si(001)materials without antiphase domains via MBE technique.The main research contents and results are presented in three parts:(1)The formation energies of antiphase domains along different propagation planes in GaAs are calculated by first principle,and the temperature dependence of the antiphase domain formation energy is analyzed to provide a theoretical explanation behind the experimental phenomenon of antiphase domain annihilation.First,the antiphase domain models propagating along the {110},{111} and {112} planes in GaAs are developed.Subsequently,the antiphase domain structures of different propagating planes are calculated using the first principle.The results indicate that antiphase domain formation energies along different propagation planes exhibit different trends with temperature.Within the 0 K-660 K temperature range,the lowest antiphase domain formation energy is noted along the {110} propagation surface,which indicates that antiphase domains preferentially propagate on the {110} surface within this temperature range.Within the 660 K-1500 K temperature range,the lowest antiphase domain formation energy values propagate along the {112} crystal plane,which implies that {112} plane is the most stable propagation plane of the antiphase domain within this temperature range.These observations indicate that the largest proportion of antiphase domains propagating along the {112} plane is noted at higher ambient temperatures.Moreover,within this temperature range,antiphase domains propagating along the {112} plane will have a higher probability of meeting and annihilating with other antiphase domains.(2)On-axis GaAs/Si materials were grown by MBE under different conditions.Results show that the antiphase domain density is lower for samples grown under higher temperatures.The antiphase domain density decreases by 42%for samples grown at 600℃ compared to those grown at 450℃.Overall,it seems that the antiphase domain density decreases with increasing growth temperatures.In addition,the number of antiphase domains propagating along the {112} surface is higher in the crosssectional region of the sample under higher growth temperatures,in which more antiphase domain annihilations noted.Therefore,growth temperature is closely related to the annihilation of antiphase domains,and a higher growth temperature induces antiphase domains to preferentially twist to the {112} crystal plane and subsequently annihilate with other antiphase domains,which is consistent with the theoretical calculation.(3)The adjustment of the surface phase of on-axis Si(001)substrate by Al atoms is investigated theoretically.Two surface phases,dimer vacancy row(DVR)and dimer vacancy column(DVL),are modeled on the Si(001)substrate surface,and the effects of different Al atom coverage on the surface energy of the two structural phases are considered.The calculation results indicate that the surface energies of DVR and DVL with different Al coverage are distinct.At a prescribed condition,the Si surface is dominated by the Al-adsorbed DVL surface,in which the Si surface is a DA-type step.This implies that Al atoms are able to adjust the Si surface phase.Since the MBE system is a vacuum environment,the pressure is close to 0.The chemical potential of Al is only dependent on ambient temperature.Within the 300 K-1500 K temperature range,the chemical potential of Al is between-5 and-0.5 eV;and within this chemical potential range,the surface energy of any adsorbed Al atom is greater than the unadsorbed surface energy.Therefore,there are no suitable conditions that enable the adjustment of Si surface phase by Al atoms within the 300K-1500K temperature range.