GaAs substrate misorientation and the effect on InAs quantum dot critical thickness

Control of InAs critical thickness (θ) is important to realizing optimized growth in quantum dot (QD) devices. Substrate misorientation can change the value of θ_c but also creates more uniform QDs in both size and distribution. This work explores GaAs p-i-n photovoltaic (PV) devices grown via organometallic vapor phase epitaxy (OMVPE) using the Stranski-Krastanov (SK) growth method on substrates misoriented 6° off (100) in the [110] direction and 2°off (100) in the [110] direction. Test structures and single junction solar cells were grown in order to study device performance through light I-V measurements and spectral responsivity (SR) as well as material properties through atomic force microcopy (AFM) and photoluminescence (PL). Results of this work show that 2° [110] sample results in lower θ_c as compared to the 6° [110] (approximately 1.8 ML verses approximately 2.1 ML). The 6° [110] substrate also showed a more uniform density and size distribution of QDs. These results are important to realizing the full benefits of QD structures such as increased optical absorption.