INFLUENCE OF DEVICE STRUCTURE AND GROWTH-CONDITIONS ON THE TUNNELING CHARACTERISTICS OF SI/SI1-XGEX DOUBLE-BARRIER STRUCTURES

We have investigated different Si/Si1-xGex hole resonant tunneling structures. We demonstrate the advantages of grading the Ge concentration in the spacer layers, which allows for a smoother potential profile in the spacer layers and a higher Ge concentration in the well, and hence higher bandoffsets. This leads to an improvement of the resonances seen in the I-V characteristics of these devices. Structures grown at different temperatures emphasize the importance of obtaining abrupt Si/Si1-xGex double barrier heterointerfaces in order to obtain good I-V characteristics. Short-term post annealing at congruent-to 500-degrees-C, well below temperatures where strain relaxation or dopant diffusion into the barrier layers occur, is shown to destroy the resonances. We believe this is due to monolayer interdiffusion at the barriers, destroying the abruptness of the interfaces.