UNAMBIGUOUS IDENTIFICATION OF X-POINT-RELATED RESONANCES IN GAAS ALAS/GAAS TUNNEL-DIODES UNDER HYDROSTATIC-PRESSURE/

We have performed detailed investigations of an asymmetrically doped G aAs/AlAs/GaAs tunnel diode in which a 2D accumulation layer forms at t he emitter/barrier interface under forward bias. The systematic applic ation of hydrostatic pressure at 77 K leads to the development of a we ll resolved peak in dl/dV in forward bias above 2 kbar. The peak shift s approximately linearly downwards in voltage as the pressure is incre ased in constant steps. Comparison with self-consistent theoretical ca lculations enables us to unambiguously identify the peak as arising fr om resonant tunnelling between the electron states in the accumulation layer and the longitudinal X-point subbands of the AlAs barrier. To o ur knowledge this is the first time that quantitative agreement betwee n theory and experiment has been achieved and places our interpretatio n beyond question. Our conclusions have important implications for the optimization of microwave diodes based on such structures.