Abstract
The paper presents the results of the application of MOCVD growth technique for formation of the GaAs/AlAs laser structures with InGaAs quantum wells on Si substrates with a relaxed Ge buffer. The fabricated laser diodes were of micro-striped type designed for the operation under the electrical pumping. Influence of the Si substrate offcut from the [001] direction, thickness of a Ge buffer and insertion of the AlAs/GaAs superlattice between Ge and GaAs on the structural and optical properties of fabricated samples was studied. The measured threshold current densities at room temperatures were 5.5 kA/cm2 and 20 kA/cm2 for lasers operating at 0.99 μm and 1.11 μm respectively. In order to obtain the stimulated emission at wavelengths longer than 1.1 μm, the InGaAs quantum well laser structures with high In content and GaAsP strain-compensating layers were grown both on Ge/Si and GaAs substrates. Structures grown on GaAs exhibited stimulated emission under optical pumping at the wavelengths of up to 1.24 μm at 300 K while those grown on Ge/Si substrates emitted at shorter wavelengths of up to 1.1 μm and only at 77 K. The main reasons for such performance worsening and also some approaches to overcome them are discussed. The obtained results have shown that monolithic integration of direct-gap A3B5 compounds on Si using MOCVD technology is rather promising approach for obtaining the Si-compatible on-chip effective light source.
Highlights
A perspective route for further progress of modern microelectronics relies on the development of the optical interconnects both between the on-chip elements and chip-to-chip links
To shift the operation wavelength of InGaAs/GaAs quantum well (QW) lasers in this spectral range it is necessary either to increase the In fraction in a QW or to increase a QW thickness
We present the results of optimization of the initial stages of growth of A3 B5 structures on Ge relaxed buffers grown on Si(001) substrates which were both exact and 4 degrees offcut toward the [011] direction
Summary
A perspective route for further progress of modern microelectronics relies on the development of the optical interconnects both between the on-chip elements and chip-to-chip links. To shift the operation wavelength of InGaAs/GaAs quantum well (QW) lasers in this spectral range it is necessary either to increase the In fraction in a QW or to increase a QW thickness In both cases, the compressive strains in the QW arise which could lead to the dislocation formation at the InGaAs/GaAs heterointerface. Due to the fact that lattice constant of GaAsP is smaller than that of GaAs, GaAsP layers create the tensile strains in a structure and so partially compensate the compressive strains in the QW This makes it possible to obtain the defect-free QWs with a larger fraction of In and so to achieve a longer-wavelength emission as compared with the “classical” InGaAs/GaAs QWs. In this paper, we present the results of optimization of the initial stages of growth of A3 B5 structures on Ge relaxed buffers grown on Si(001) substrates which were both exact and 4 degrees offcut toward the [011] direction. The opportunities to achieve the high In content QWs in the lasers active area which emit light at wavelengths longer than 1.1 μm with the help of strain-compensating GaAsP layers were investigated
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