Nanoscale Studies of Energy Band Gaps and Band Offsets in Compound Semiconductor Heterostructures.

Nanoscale Studies of Energy Band Gaps and Band Offsets;Engineering;Materials Science and Engineering

Chang, Alexander S.Clarke, Roy ;

University of Michigan

关键词: Nanoscale Studies of Energy Band Gaps and Band Offsets;    Engineering;    Materials Science and Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/120730/asjang_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The identification of the precise band offsets at semiconductor interfaces is crucially important for the successful development of electronic and optoelectronic devices. However, issues at the interfaces, such as strain or defects, needs to be investigated for precise band tuning of semiconductor heterostructures. In this dissertation, the nanometer-scale structural and electronic properties of InGaAs(Sb)N/GaAs interfaces, InGaN/GaN QDs, and GaSb/GaAs QDs are investigated using a combination of XSTM and STS.The influence of Sb incorporation on the InGaAs(Sb)N/GaAs band alignment is investigated. At the InGaAsN/GaAs (InGaAsSbN/GaAs) interfaces, type II (type I) band offsets are observed, due to strain-induced splitting of the valence band and the incorporation of Sb. Band tuning of both conduction and valence band edges with the incorporation of Sb can be used to engineer the band structure with strong confinement of electrons and holes in the InGaAsSbN quantum well layer, which is promising for light emitting applications.The influence of the growth substrate on InGaN/GaN QD formation and properties is examined. The QD density, dimension, and band gaps are compared for different InGaN QDs on free-standing GaN or GaN/AlN/sapphire substrates. We present different sources using nucleation on different substrates, and discuss their influences on the electronic band structure. Our work suggests that a wide variety of InGaN QD dimension, density, and band structure can be achieved by using different starting substrate and number of layers of InGaN QD stacks. Furthermore, the influence of strain and dislocation on the GaSb/GaAs QD band alignment is investigated using both experimental and computational tools. A combination of cross-sectional transmission electron microscopy (XTEM), XSTM, and STS reveals the formation of misfit dislocations and both coherent and semi-coherent clustered QDs, independent of Sb- vs. As-termination of the GaAs surface. Furthermore, finite element analysis simulation on GaSb/GaAs QD band alignment reveal that the dislocation and misfit strains in the vicinity of GaSb/GaAs QD interfaces lead to a transition from type I to type II band offsets.