Ballistic transport of hot electrons and intervalley resonant tunneling in semiconductor quantum well heterostructure devices

In semiconductor quantum well tunneling structures, a significant number of carriers can ballistically traverse the active device region. Ballistic electrons can attain energies greater than the direct-gap conduction band minima of all material layers or can transfer to satellite valleys. Experimental investigation of intravalley and intervalley transport of hot electrons in GaAs/AlGaAs/AlAs and InAs/AlSb based vertical resonant tunneling structures was the subject of this research. The objective of the thesis was to study all possible resonant and non-resonant intervalley processes of importance to quantum well tunneling structures, particularly those involving excited quasi-bound states in X-point quantum wells, and to study the influence of these intervalley processes on intravalley device characteristics and design. External transverse magnetic fields tuned the incident electron energy by redistributing carrier momentum. Externally applied hydrostatic pressure and uniaxial stress altered the band structure and were used to identify, induce, and enhance intervalley tunneling resonances. Device modeling by self-consistently solving the Poisson equation and the one-dimensional Schrodinger equation accounted for space charge build-up and non-linear potential drops enabling accurate device design and analysis. Use of these tools allowed observation of ballistic electron induced switching of vertically integrated resonant tunneling diodes, determination of material properties high above the band edge, elucidation of all possible intervalley tunneling paths and their effect on intravalley device characteristics, and the demonstration of a new intravalley device relying on hot ballistic resonant transport, the electron wave interference diode. Since elastic intervalley tunneling can occur even for perfectly grown heterostructures, design of heterostructure devices must include analysis of all possible tunneling paths. By understanding such design implications, quantum well tunneling structures relying on energetic carriers can serve as specialized functional devices in the continued evolution of microelectronics.