Cross-Sectional Scanning Tunneling Microscopy Investigations of Cleaved Iii-V Heterostructures

Abstract

Fabrication technology and device sizes have reached the point where fluctuations on the atomic level may affect device performance. The need for a tool to characterize these structures has been satisfied by cross-sectional scanning tunneling microscopy (XSTM). This thesis details the development and application of XSTM to III-V heterostructures. An ultra-high vacuum (UHV) system dedicated to XSTM has been specifically designed and constructed as part of this work. Reported for the first time are XSTM cross-sections of self-assembled InAs quantum dots, XSTM cross-sections of quantum wires created by the strain-induced lateral-layer ordering (SILO) process as well as the first XSTM data on working device structures. These working device structures include a few resonant tunneling diode (RTD) structures, a quantum well infrared photodetector structure and a modulation doped field effect transistor (MODFET) structure. XSTM has proved useful in characterizing interface roughness, alloy fluctuations and individual atomic positions.