Jackson State University
Faculty Sponsor's Department(s):
Electrical and Computer Engineering
Characterization of InN Quantum Dots
Epitaxial quantum dots (QDs) can be used in the active regions of light-emitting diodes (LEDs) and laser diodes (LDs). The focus of this study was infrared emitting InN QDs grown on GaN for use in infrared optoelectronic devices. This process was difficult since the two components, InN and GaN, have different growth temperatures and lattice constants. GaN is typically grown at 1200°C and InN is grown at 600°C, with the materials having a lattice mismatch of greater than 10%. This work concentrates on the growth of InN QDs by metalorganic chemical vapor deposition (MOCVD) at low growth temperatures and the subsequent characterization of the QDs. MOCVD was used to grow InN QDs, on top of MOCVD-grown GaN-on-sapphire substrates. The samples had different nominal thickness, which refers to how thick a layer would be if the material were to grow as a planar layer rather than as QDs. We used atomic force microscopy (AFM) to get images of the QDs, then calculated the amount of material deposited (layer thickness) from the AFM images. After that, we compared the calculated layer thickness to the expected values (nominal thickness). For most samples, the calculated values were much larger than the expected values, up to an order of magnitude greater. For example, one sample had a nominal thickness of 0.50 nm, but the layer thickness was 5.41 nm. This difference between the expected value and the calculated value may be due to factors such as, the calibrated growth rate being too low, the AFM not resolving the QDs well, and the assumptions made in calculations. Future studies, such as comparing the size of the QDs by AFM to other more advanced microscopy techniques such as scanning transmission electron microscopy (STEM), may address the discrepancies found here.