Molecular beam epitaxial growth of III-V semiconductor ... - KOBRA

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Optimization of MEE and MBE growth of GaP Buer on Silicon Substrate were varied while maintaining a 100 nm/h growth rate, as was done during the GaP/GaP homoepitaxy growth optimization [136]. The GaP-MBE/GaP-MEE/ Si was grown on cleaned silicon substrate as described in Sec. 7.3 in conjunction with GaP-MEE growth procedure discussed in Sec. 7.4.1. AFM and RHEED analysis were used to verify the 2D planar growth and investigate the surface morphology of the dierent GaP growth modes. 7.5.1 Growth Temperature of MBE-GaP After the growth of the rst 10 nm GaP using the MEE-mode, the growth temperature of the MBE step was varied with a narrow range of 20 K from the standard growth temperature of GaP on GaP substrate in the MBE-GaP growth [136]. The Ga growth rate used for the MBE was the same as for the MEE step (100 nm/h) and P 2 /Ga ratio was set to 15. Two samples were overgrown with 40 nm GaP (nominal thickness) at two dierent growth temperatures of 545 ◦ C and 560 ◦ C, respectively. The surface reconstruction during MEE and MBE GaP epitaxy was in-situ monitored with by RHEED. Note that between MEE-GaP growth step and MBE-GaP growth there is a growth stop, where the substrate temperature was ramped up from 350 ◦ C (MEE-step) to the MBE-GaP growth temperature with a ramp rate of 50 K/min. Figure 7.4: Reection high energy diraction patterns of GaP growth on Si(100). (a) Streaky RHEED pattern during MEE-mode indicating a 2D planar growth. (b) Spotty RHEED pattern during MBE-mode indicates a non-planar surface morphology. 122
7.5 Optimization of MEE Followed by MBE Growth of GaP Buer on Si Substrate Streaky RHEED pattern was observed during MEE-GaP growth till the rst stage of MBE-GaP growth step indicating a 2D planar growth scenario for the rst 10 nm GaP-MEE as shown in Fig. 7.4(a). Streaky RHEED patterns were observed during the temperature ramping from 350 ◦ C till the MBE growth temperature of 560 ◦ C. At the GaP-MBE growth temperature and after a few nm GaP depositions spotty RHEED patterns are observed indicating a non-planar growth (Fig. 7.4(a)). The transition from streaky to spotty RHEED patterns, means the MBE-GaP growth step still need further optimization. The AFM images (Fig. 7.5) of the MBE-GaP growth conrmed a rough surface prole with some hole like structures or connected GaP islands. Figure 7.5: (5 × 5 µm 2 ) AFM images of 40 nm GaP-MBE/10 nm GaP-MEE /Si at dierent growth temperatures. (a) 545 ◦ C with RMS = 6 nm, (b) 560 ◦ C with RMS = 8.2 nm. However, the smoother surface with reduced roughness of 6 nm (RMS value) was obtained at a GaP-MBE growth temperature of 545 ◦ C as shown in Fig. 7.5(a). Decreasing the MBE-GaP growth temperature below 545 ◦ C or increasing above 560 ◦ C resulted in similar surface morphology. In both cases the nal surface roughness of the best result we report here approximately is doubled. As we already mentioned that during GaP/GaP homoepitaxy optimization not only the growth temperature was investigated but also the V/III ratio. Therefore, new series of samples with dierent P 2 /Ga ratios still have to be investigated. 123
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Molecular Beam Epitaxial Growth of
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Gutachter (Supervisors): 1. Prof. D
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patterns indicating a 2D smooth sur
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(MEE = migration enhance epitaxy) u
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CONTENTS 3.4.4 Planar Defects Assoc
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CONTENTS xii
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Introduction thesis a detailed stud
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Introduction 1.1.2 Thesis Approach
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Introduction 1.2 Thesis Outline The
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Theoretical Background of Semicondu
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Heteroepitaxial Growth of III-V Sem
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Experimental Growth and Characteriz
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MBE Growth of Self-Assembled InAs a
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Page 86 and 87: MBE Growth of Self-Assembled InAs a
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Page 144 and 145: REFERENCES [8] J. M. Gerard, O. Cab
Page 146 and 147: REFERENCES [29] http://www.wmi.badw
Page 148 and 149: REFERENCES [49] M. R. Brenner: GaP/
Page 150 and 151: REFERENCES [66] Y. Ishida, T. Takah
Page 152 and 153: REFERENCES [84] A. Garcia, C. M. Ma
Page 154 and 155: REFERENCES [100] M. Felici, P. Gall
Page 156 and 157: REFERENCES [116] H. Usui, H. Yasuda
Page 158 and 159: REFERENCES [133] Grassman, T. J. Br
Page 160 and 161: Conferences Contributions: Tariq Al
Page 162 and 163: Nomenclature
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Molecular beam epitaxial growth of III-V semiconductor ... - KOBRA

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