Optical and structural behaviour of InAs quantum dots grown on the Si substrate without Si-Ge graded layer and without Migration Enhanced Epitaxy layer

摘要

Self-assembled Ⅲ-Ⅴ compound semiconductor quantum dots (QDs) on silicon (Si) substrate is much explored topic for optoelectronic devices. Here, we have investigated the optical and structural behavior of InAs QDs grown on (001)-oriented Si substrate. The heterostructure has been grown without Si-Ge buffer/graded layer and without Migration Enhanced Epitaxy layer which might reduce the anti-phase domain and dislocation propagation towards the active region. The heterostructure grown on Si (sample A) consists of a thick GaAs buffer layer which was followed by AlAs/GaAs super-lattice buffer layer and three consecutive layers of 2.7 ML InAs QDs with 50 nm GaAs capping. A heterostructure with similar active layers was grown on GaAs substrate (sample B). Samples were characterized using photoluminescence (PL) and high resolution X-ray diffraction (HRXRD) measurements. Sample A exhibited blue-shifted PL peak as compared to sample B, which might be due to the forrnation of smaller dots. Moreover, from the power-dependent PL analysis, a multimodal and bimodal dot size distribution was observed in sample A and B respectively. HRXRD measurements showed the poor crystalline quality in sample A as compared to sample B. However, PL of sample A exhibited a higher intensity in comparison to sample B. In addition, sample A provided higher activation energy of 290 meV, whereas it was 198 meV in case of sample B. This indicates better confinement of charge carriers, which might improve the device performance. The optoelectronic performances could be enhanced by further optimizing this growth strategy through optimizing the dot layer periodicity, capping material, and capping thickness.