MOCVD Growth of InGaAs/GaAs/AlGaAs Laser Structures with Quantum Wells on Ge/Si Substrates

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