Realization of high-quality InGaAs/GaAs quantum dot growth on Ge substrate and improvement of optical property through ex-situ ion implantation

Abstract

Epitaxial growth of III-V heterostructures on non-native substrates such as Silicon (Si) or Germanium (Ge) is one of the promising research topics for the last two decades. The interface between polar III-V semiconductors and non-polar substrates (Si or Ge) plays a crucial role in monolithic integration. However, there is an anticipation of epitaxial GaAs growth on Ge substrate because of the lower mismatch of lattice constants and thermal expansion coefficients between them. Therefore, the high-quality growth of III-V semiconductor heterostructures on Ge substrates would overcome the impediment to Si-photonics, where the monolithic integration of optoelectronic device structures can be done using a Ge graded layer on Si. Here, we have explored the epitaxial growth of multi-layer InGaAs/GaAs quantum dot heterostructures on Ge substrates and compared the optical and structural properties with the QDs grown on GaAs substrate. The optical properties of all samples are investigated with the help of photoluminescence (PL) and time-resolved photoluminescence (TRPL), whereas the morphology of the QDs is observed through cross-sectional transmission electron microscopy (XTEM) images. An enhancement in the optical characteristics (PL peak wavelength, activation energy, carrier lifetime) is found for the QDs grown on Ge substrate with the super-lattice buffer (SLB) layer. The minimization of defects and dislocations in the heterostructure is also realized for the structure with the SLB layer. Furthermore, a two-fold enhancement in PL intensity and 24 meV increment in activation energy is achieved through ex-situ H− ion-implantation, which approached the values obtained for the QD heterostructure grown on GaAs substrate.