Electron transport in rectifying semiconductor alloy ramp heterostructures

The electron transport properties of AlGaAs ramp diodes are investigated using a physical model which combines current transport through the heterostructure bulk with current across the abrupt heterointerface in a fully self-consistent numerical approach. Transport at the abrupt material discontinuity is described by thermionic and thermionic-field emission processes, whereas transport in regions of smoothly varying alloy composition is modeled by diffusion-drift mechanisms. Several devices whose bandgaps are graded over several thousand angstroms have been fabricated by molecular beam epitaxy (MBE) and tested at room and liquid-nitrogen temperatures. The experimentally observed rectification properties are compared with the simulated results over a wide range of DC bias. Through appropriate choice of alloy composition and doping profiles, majority carrier devices based on internal (bulk) barriers may be realized