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 7.5.2 P 2 /Ga Ratio of MBE-GaP In this study all other parameters remain xed like gallium growth rate of 100 nm/h and growth temperature of 545 ◦ C. A 40 nm thick GaP layer as grown Figure 7.6: (5 × 5 µm 2 ) AFM images of 40 nm GaP-MBE/10 nm GaP-MEE /Si with dierent P/Ga ratios . (a) 10 with RMS = 7.4 nm. (b) 15 with RMS = 6.8 nm. (c) 20 with RMS = 8.7 nm. (d) 25 with RMS = 12.5 nm. in MBE mode on top of a 10 nm thick GaP layer grown on Si by MEE mode (350 ◦ C) with dierent P 2 /Ga ratios ranging from 10 to 30 (Fig. 7.6). The GaP/GaP homoepitaxy experiments indicate that a P 2 /Ga ux ratio about 9:1 should provide acceptable quality GaP epilayers while growing at 550 ◦ C substrate temperature and a 100 nm/h growth rate [136]. However, the AFM analysis in Fig. 7.6 showed that the smoother surface with the best RMS value was obtained with P 2 /Ga ratio of 15:1 (Fig. 7.6(b)) using the same growth conditions. However, the RMS value is still relatively high after these investigations. However, all previous investigations were conducted with growth stop between the two growth modes, i.e, during the temperature ramping from MEE-GaP growth (at 350 ◦ C) 124
7.5 Optimization of MEE Followed by MBE Growth of GaP Buer on Si Substrate to MBE-GaP growth (at 545 ◦ C). Using the same growth conditions described for the best RMS value in Fig. 7.6(b). Another two samples were grown with and without growth stop between MEE and MBE modes. The sample without growth stop between the two modes (Fig. 7.7(b)) showed an improved RMS value of 3.2 nm, which is almost half the RMS value compared with the sample with growth stop between the two modes (Fig. 7.7(a)). Figure 7.7: (5 × 5 µm 2 ) AFM images of 40 nm GaP-MBE/10 nm GaP-MEE /Si. (a) With growth stop (RMS = 6.8 nm). (b) Without growth stop (RMS = 3.2 nm). An additional improvement was achieved with the increased Ga growth rate from 100 nm/h (MEE-GaP growth step) to 300 nm/h (MBE-GaP growth step)). By applying the same growth conditions used in Fig. 7.7 and increasing the Ga growth rate from 100 nm/h during MEE growth to 300 nm/h during MBE growth, a smooth surface with a very good RMS value of 1.3 nm was observed (Fig. 7.8). In addition, when comparing GaP-MBE/GaP to GaP-MBE/GaP- MEE/Si, it is clear that optimum MBE growth parameters are very similar, if not identical. We interpret this to mean that the GaP/Si formed after the above described MEE process has generated an eective GaP growth template on Si, since the presence of Si does not require alteration of the standard GaP epitaxy parameters. However, our optimizations are done for a very thin GaP layer with ∼ 50 nm nominal thickness. The best RMS value of 1.3 nm for the MBE-GaP growth was obtained without growth stop, and with the increased Ga growth rate from 100 nm to 300 nm during the temperature ramping from MEE to MBE growth mode. 125
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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 144 and 145: REFERENCES [8] J. M. Gerard, O. Cab
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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
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Molecular beam epitaxial growth of III-V semiconductor ... - KOBRA

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