分子束外延GaAs/Si(001)材料反相畴的湮灭机理

Annihilation Mechanism of Antiphase Domains in GaAs/Si(001)Materials Grown by Molecular Beam Epitaxy

从第一性原理出发,计算了不同温度下GaAs材料中沿{110}、{111}和{112}面传播的反相畴(APD)形成能,探索了反相畴的湮灭机理。结果表明,当温度达到660 K以上时,APD最稳定的传播晶面从{110}转变到{112}。通过分子束外延(MBE)技术,在无偏角Si(001)衬底上生长了1.4μm厚的GaAs外延层。测试结果表明,随着生长温度的升高,APD密度降低,不同传播面的湮灭现象增加。反相畴在较高的生长温度下更易于扭折到{112}面,从而与其他反相畴相遇并发生湮灭。该结果对全MBE生长高性能无偏角硅基激光器研究具有重要意义。

Objective Anunprocessed,on-axis Si substrate has a single-layer atomic step structure on its surface.The epitaxial growthofⅢ-Ⅴmaterials on substrates results in the high-energy planar defect called antiphasedomain(APD).The APD reduces the minority carrier lifetime in devices,degrading the performance of devices.Placing an on-axis Si substrate in the hydrogen environment for high-temperature annealing can promote the transformation of single-layer atomic steps into double-layer atomic steps and suppress APD generation at the Ga As/Si interface.However,the molecular beam epitaxy(MBE)technology cannot take hydrogen as annealing environment.Existing experimental methods involve changing the experimental process,which is unique and difficult to reproduce,to promote the annihilation of APD in Ga As materials.However,the APD annihilation mechanism remains unclear.In this study,the formation energyof APD propagating along the{110},{111},and{112}planes in Ga As materials at different temperatures is calculated using the first principle to explore the APD annihilation mechanism.The most stable propagating plane of the APD changes from{110}to{112}when the temperature exceeds 660 K.A 1.4-μm thick Ga As epitaxial layer is grown on an on-axis Si(001)substrate using the MBE technology.The results demonstrate that the APD density on the Ga As surface decreases and the annihilation probability of the APD increases with an increase in the growth temperature.At high growth temperatures,the APD can easily be twisted to the{112}plane and annihilate.Methods Aiming at the phenomenon of APD kink and annihilation in on-axis Ga As/Si(001)epitaxial materials,this paper presents the detailed exploration and analysis of theoretical simulations and experiments,respectively.According to the different propagation planes of the APD in Ga As,APD models propagating along the{110},{111},and{112}planes are established.The APD formation energy on these three propagation surfaces and their variation trends with temperature are obtained using the first principle.Experimentally,Ga As epitaxial layer is grown on an on-axis Si(001)substrate based on the MBE technology using a three-step method.Atomic force microscopy(AFM)and transmission electron microscopy(TEM)are used to characterize the surfaces and cross sections of the samples.Results and Discussions The APD formation energy on different propagation planes varies with temperatures.At0--660K,the APD formation energy on the{110}propagation plane is the lowest,and at 660--1500K,the APD formation℃,the higher the growth energy on the{112}propagation plane is the lowest(Fig.3).In the range of 450--600temperature,the lower the APD density(Fig.5)and the higher the APD annihilation degree in the sample(Fig.6),which is consistent with the calculated results.Conclusions In this study,the formation energy of APDs propagating along the{110},{111},and{112}planes in Ga As is calculated based on the first principle,and the effect of growth temperature on the APD formation energy in vacuum environment is determined.The theoretical results demonstrate that,at 0 K,the formation energy of the APD propagating along the{110}plane is the lowest;in the temperature range of 0--660K,the formation energy of the APD propagating along the{110}plane is the lowest;and in the temperature range of 660--1500K,the APD propagating along the{112}plane has the lowest formation energy.The experimental results demonstrate that when the temperature increases from 450℃to 600℃,the APD density decreases by 42%,and in the sample with a growth temperature of500℃,more APDs along the{112}plane are found to meet other APDs and annihilate.A higher growth temperature promotes the kink of the APD to the{112}plane and then the APD annihilates in the Ga As material with a certain thickness,which is consistent with the theoretical calculation results.In this study,based on the first principle and MBE technology,experimentally the propagation characteristics of APD in on-axis Ga As/Si(001)materials are theoretically analyzed and verified.The results have a guiding significance for the experimental process exploration of growing high quality APD-free Ga As materials on on-axis Si(001)substrates by MBE technology and promote the research on highperformance on-axis silicon-based lasers by MBE technology.