Dr. Tang Xiaohong, Associate Professor, School of Electrical & Electronic Engineering, Nanyang Technological University, Singapore

Title: High quality InP based III-V compound semiconductor mid-IR quantum dots

Abstract: Semiconductor quantum dot (QD) structure based optoelectronic devices, e.g. semiconductor lasers, show many advantages as compared with their counterpart quantum well based devices, including ultra-low threshold current density, temperature stable and high differential gain. In this work, compound semiconductor QDs emitting up to longer wavelength than 2.8um have been prepared by using metal-organic chemical vapour deposition (MOCVD). With a two-step growth method, the grown QD density has been increased more than 30% as compared with that grown by using normal Stranski-Krastanow self-assembled growth method. Using this two-step growth method, the size uniformity and the QD morphology have been improved much. Emission wavelength of the InAs QDs has been extended by embedding them in the graded InGaAs matrix layers. The emission wavelength of the InAs/InGaAs QDs structure red shifted 370nm when embedded the InAs QDs in the graded In0.53-0.8Ga0.47-0.2As barriers. The longest emission wavelength of the QD structure was measured >2.35um at 77K. MOVPE growths of InAsSb QDs on InP have been developed for the longer wavelength emission. High QD density, up to 1.3x1010 cm-2, of the InAsSb QDs grown on InP has been achieved. The longest emission wavelength of the InAsSb QD structure reaches >3.4um.

Post-growth bandgap shift of the QD structure has been investigated. Very large blue shift up to >160meV of the QD structure has been achieved.

It is acknowledged the MOE of Singapore for sponsoring this research, RG176/16

Keywords: III-V semiconductor, quantum dot, mid-infrared, MOCVD