Microprobe investigations of semiconductor structures

• Main Author: Miles, Robert J.
• Format: Others
• Language: en
• Published: 1995
• Online Access: https://thesis.library.caltech.edu/4144/1/Miles_rj_1995.pdf; Miles, Robert J. (1995) Microprobe investigations of semiconductor structures. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/7bk3-4486. https://resolver.caltech.edu/CaltechETD:etd-10172007-144050 <https://resolver.caltech.edu/CaltechETD:etd-10172007-144050>

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. This thesis describes the results of experimental studies of semiconductor structures using local microprobe techniques. The studies primarily concern two questions: the detection of local variations in material quality and transport properties, and the control of material preparation and growth to minimize these variations. In chapter 2 we investigate the source of defects in nitrogen-doped ZnTe grown on ZnTe and GaSb substrates. Through the use of atomic force microscopy (AFM) and transmission electron microscopy (TEM), we find that defect generation is minimized on GaSb substrates with nitrogen delta-doping. Using selective etching techniques, we also show that the Zn {111} fault planes tend to originate at the doping layers while Te {111} fault planes tend to originate at the substrate/epilayer interface. A simple doping model from Chadi et al., explains the observed effect. In chapter 3 we studied the effects of electron-beam-assisted molecular beam epitaxy (EB MBE) on the growth of Si on [...]/Si(111). By irradiating the surface of [...] with low energy electrons, the surface free energy of the [...] is raised and the subsequent Si layer is smoother. By using AFM, X-ray diffraction, and XPS, we find that an optimal range of exposures exist that minimizes surface roughness and we present a simple thermodynamic model to explain this. We further show that for temperatures below the epitaxial growth temperature of Si (500°C), the irradiation causes a transition in the Si grown from amorphous to ordered. In chapter 4 we investigate the electrical properties of the intrinsic ZnTe(110) surface. Using scanning tunneling microscopy (STM) and spectroscopy, we find a new criterion for determining the extent of Fermi level pinning. This criterion involves observing the enhancement of reverse bias current with increasing tip-sample separation. The mechanism is an increase in the tunneling transmission of carriers through the semiconductor's space charge region that more than compensates for the reduced tunneling transmission through the tip-sample gap as the tip retracts from the surface. We also find that upon subsequent exposure of the surface to contaminates, the surface becomes pinned. Chapter 5 describes our ballistic electron emission microscopy (BEEM) investigations of semiconductor structures. We describe our studies of Au/Si(100) interfaces and show that the barrier height extracted from the spectroscopy using a simple model agrees well with the known Au/Si Schottky barrier height. We also present preliminary studies of InAs/AlAs/GaAs single barrier structures. Through frequency plots we feel we can confidently identify transport associated with specific local band structure, particularly the GaAs and AlAs [...]-pt. Finally, in Appendix A we discuss the contemporary STM theories along with the theory we used for our calculations in chapter 4. In Appendix B, we discuss in detail the construction of BEEM equipment along with its operation.