Development of SiGeSn IR Detectors

Student: Justin M. Rudie

Degree: M.S., Dec. 2021

Major Professor: Dr. Fisher Yu

Research Area(s):

Nanoscale Materials & Devices

Microelectronic-Photonic Materials & Devices

Current infrared imaging sensors are expensive III-V materials
Germanium based materials are well suited for IR detection, but material systems are relatively unexplored/characterized
Characterization of band offsets is necessary for device modeling to advance this material system.

Novel CVD growth techniques to increase Sn in previously unrealized compositions of SiGeSn will be grown and characterized
Band offsets of SiGeSn/Gesn will be determined

CVD growth plans altering pressure, temperature, growth time and other parameters to achieve quality samples
Confirmation of material content and quality via ellipsometry, PL, TEM imaging, etc.
XPS of multiple samples to find core level binding energies leading to the determination of the valance band offset (VBO) of the heterojunction.
Equation to determine VBO:∆E_V=(E_aⁱ – E_bⁱ) + (E_CL^b – E_VBM^b) – (E_CL^a – E_VBM^a)
Conduction band offset (CBO)can be determined from band gap data after VBO is known.

Currently finding offsets of Ge/Si and Ge/GaAs to compare with literature to validate method
Results are in the form: Reference value/My values/Difference
Ge/Si VBO = 0.37 eV compared to 0.83 eV in literature
Ge/GaAs VBO = -0.4 eV compared to 0.56 eV in literature

So far method has not been able to recreate know offsets of Ge/Si and Ge/GaAs materials.
Native oxide present a serious obstacle for finding actual binding energies

Comprehensive sample prep method to ensure oxide free surface without crystal damage
Proceed with measurements on GeSn/Ge and SiGeSn/GeSn samples.