Magnetic field effects and k∥-filtering in BEEM on GaAsAlGaAs resonant tunneling structures

Abstract

In this work, GaAs-AlGaAs double barrier res- onant tunneling diodes (RTDs) are investigated by ballistic electron emission microscopy (BEEM). RTDs grown directly below the sample surface exhibit characteristic steplike fea- tures in the BEEM spectrum, whereas for buried RTDs, a lin- ear spectrum is observed. Moreover, the BEEM spectra of sub-surface RTDs show Shubnikov-de Haas-like oscillations in magnetic fields. To investigate the origin of these effects, the BEEM spec- tra were calculated using a scattering formalism within the framework of a semi-empirical tight binding method. As a main result we found that, independent of the applied bias, only electrons within a narrow kdistribution are transferred resonantly through the RTD. Hence, a kfilter is established for ballistic electrons close to k� = 0. The calculated filter width is consistent with the magnetic field data.