RESONANT-TUNNELING BETWEEN TRANSVERSE-X STATES IN GAAS ALAS DOUBLE-BARRIER STRUCTURES UNDER ELEVATED HYDROSTATIC-PRESSURE/

We present a model to describe the mechanisms involved in tunneling be tween the quasiconfined X subbands of the AlAs layers in GaAs/AlAs dou ble-barrier structures at pressures up to the type-II transition. The model involves self-consistent Schrodinger-Poisson calculation of the potential profiles within the device for a given relative alignment be tween the two X-like quantum wells,;md thus allows prediction of the b ias positions at which certain resonant tunneling processes will occur . By systematic variation of the parameters involved, in particular th e charge distribution between the two AlAs layers, these predictions h ave been fitted to the measured vertical transport characteristics of a series of samples of different AlAs layer width. In the cases of tho se samples with X ground states that are transverse in nature, very go od agreement has been obtained. The level of insight afforded by the m odel opens up alternative methods for the determination of important b and-structure parameters. such as the light effective mass of the X mi nima in AlAs, and tile Gamma(GaAs)-X-AlAs conduction-band offset. It a lso proves to be an extremely sensitive probe of the degree of symmetr y between the AlAs layer widths of near-symmetric devices, and we are thus able to measure an asymmetry of around one monolayer in each of o ur devices. This explains entirely the asymmetry exhibited by the low bias X-t(1)-->X-t(1) resonances of some nominally symmetric double-bar rier structures, which has been a source of some debate in recent year s.