Intermediate-band solar cells based on InAs submonolayer quantum dots grown with a (2x4) surface reconstruction

• Grant number: 23/10255-8
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: November 01, 2024
• End date: October 31, 2026
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Alain André Quivy
• Grantee: Ahmad Al Zeidan
• Host Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

In this project, Dr. Ahmad Al Zeidan will optimize a new technique for growing submonolayer quantum dots (SMLQDs) of InAs. The novelty consists in depositing the SMLQDs in the presence of a (2x4) surface reconstruction in order to nucleate two-dimensional (2D) InAs islands of good quality that are the building of blocks SMLQDs. However, instead of lowering the sample temperature to 500 °C to deposit the InAs material-which leads to a c(4x4) reconstruction-and then lowering the arsenic flux to recover a (2x4) reconstruction, as we have been doing in recent years, we will use a new approach. The temperature will be reduced less than before (525 °C) in order to maintain a (2x4) reconstruction and prevent it from changing to c(4x4). In this case, it will no longer be necessary to decrease the arsenic flux, which will allow reaching a high Indium content in the samples, unlike what happened with the previous technique. This new type of SMLQDs will be used in the middle of a GaAs solar cell to enable the absorption of radiation having energy lower than the GaAs band gap. We therefore hope to manufacture, for the first time, an intermediate-band photovoltaic cell with higher conversion efficiency than its conventional counterpart.