Low Temperature Growth of Group IV Materials for Optoelectronics Applications
Student: Oluwatobi G. Olorunsola
Degree: Ph.D., December 2021
Major Professor: Dr. Fisher Yu
Current solar photovoltaic systems have seen significant improvements in recent years but most still grapple with drawbacks ranging from excessive cost to lagged performance.
A new group IV alloy SiGeSn thin film is proposed to address these issues through the growth of high quality, lattice-matched, tunable band gap, and CMOS compatible material for improved solar efficiency.
Explore innovative growth techniques to reduce defects for material integration of GeSn and other group IV alloys on Si.
- Growth of group IV alloys in a hot wire plasma enhanced cold walled UHV-CVD using precursor gases.
- Investigate Sn droplet formation on grown alloy films.
- Characterize materials using PL, Ellipsometry, Raman Spec., XRD, TEM and other material characterization tools.
- Optimize growth recipes to produce substrate quality GeSn virtual substrate.
- Growth of solar multi-junction heterostructures.
- One/two-step Ge-buffer films and plasma-enhanced growth has been demonstrated at low temperatures.
- Sn phase segregation were observed on select samples at certain growth conditions.
- Investigated specific growth conditions sponsoring Sn phase segregation effects.
- Sn droplets population were seen to reduce following an etching procedure.
Findings from previous growth efforts reveals the impact of optimized growth temperatures and Sn overpressure on material quality [Grant et al, 2018].
On-going Sn-droplets segregation analysis could provide details on extent of impending limitations posed to underlying growth layers.
- Characterize and compare before and after etching outcomes.
- Optimize growth conditions for enhanced material quality on:
- GeSn on Ge buffered Si.
- Plasma enhanced GeSn on Ge buffered Si