Growth of BxGa1−xAs, BxAl1−xAs and BxGa1−x−yInyAs epilayers on (0 0 1)GaAs by low pressure metalorganic chemical vapor deposition
Introduction
It is well know that boron (B) has been widely used as the p-type dopant in silicon-based microelectronic industry for several decades. Encouragingly, incorporation of boron atoms into conventional III–V compounds such as GaAs to synthesize new boron-incorporated materials has received considerable attentions, due to their potential applications in the field of bandgap engineering, strain compensation and optoelectronic integration, etc. In parallel with the theoretical investigations of band structures of new boron-incorporated alloys, there emerged some experimental attempts to grow theses materials. In particular, in the past few years, zinc-blende BGa(In)As alloys with boron content up to several percents have been successfully grown on GaAs by metalorganic chemical vapor deposition (MOCVD) [1], [2], metalorganic vapor phase epitaxy (MOVPE) [3], [4], and molecular beam epitaxy (MBE) [5], [6], [7]. In addition, application of BGaInAs lattice-matched to GaAs for high-efficiency solar cells has also been demonstrated [8], [9]. However, growth mechanism, boron incorporation behaviors and key properties of the promising boron-incorporated alloys are still not very clear because the corresponding experimental studies are just at the initial stage.
In this paper, we have investigated LP-MOCVD growth of zinc-blende BxGa1−xAs, BxAl1−xAs, BxGa1−x−yInyAs and relevant MQW structures on GaAs using triethylboron as boron precursor. We have studied the influence of growth parameters on boron incorporation behaviors. BxGa1−x−yInyAs epilayer with the 11 K emission wavelength of 1.24 μm was demonstrated for the first time.
Section snippets
Experimental procedure
In this study, zinc-blende BxGa1−xAs, BxAl1−xAs and BxGa1−x−yInyAs epilayers have been grown on exactly-oriented (0 0 1)GaAs substrates by LP-MOCVD. GaAs substrates were positioned in the recessed wafer pockets on a SiC-coated graphite susceptor, which was heated by three separate graphite radial heating zones. Triethylboron TEB, trimethylaluminium (TMAl), trimethylgallium (TMGa) and trimethylindium (TMIn) were used as group III sources. Pure arsine (AsH3) was used as group V source. Pd-cell
BGaAs
If the lattice constant of zinc-blende BAs is assumed to be 4.777 Å [10], the lattice constant of ternary BxGa1−xAs can be expressed as aBGaAs(x)=5.6533−0.8763·x by Vegard's law. Assuming the 100% relaxation of BxGa1−xAs epilayer and BAs Poisson ratio of 0.3, the boron composition (x) could be calculated from the DCXRD patterns.
Our experimental results indicated that boron incorporation into GaAs strongly depended on the growth temperature (Tg) and gas phase TEB mole fraction (Xv). Fig. 1 shows
Conclusion
In conclusion, we have demonstrated LP-MOCVD growth of zinc-blende BGaAs and BAlAs epilayers with the respective boron composition up to 5.8% and 1.3% on (0 0 1)GaAs substrates. It has been found that boron incorporation into GaAs and AlAs strongly depended on the growth temperature and initial gas phase mole flowrate of TEB. The experimental results show that 580 °C should be the optimum growth temperature for the deposition of both BGaAs and BAlAs using TEB source. We have also observed that
Acknowledgements
This work was supported by the National Basic Research Program of China (No.2003CB314901), the 111 Program of China (No.B07005), Program of Key International Science and Technology Cooperation Projects, MOST (No.2006DFB11110) and Program for Changjiang Scholars and Innovative Research Team in University, MOE (No. IRT0609).
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