Effective-mass wave-matching theory for a two-band Wannier system

In this paper, the effective-mass wave-matching theory for the interface of single tridiagonal band systems is extended to a two-band Wannier system. Within the context of the effective-mass wave-matching theory, the four ind ependent coupling parameters of the two coupled tridiagonal bands system ar e reduced to a single parameter. The impact of this coupling parameter and also of the transverse energy upon the transmission of electrons in resonan t tunneling diodes in such systems is demonstrated for the case where the t wo-band model represents the Gamma and X valleys of the conduction band. A multiband density of states is derived to facilitate the location in space and energy of both the resonant tunneling and Gamma-X resonances and antire sonances. To qualify the application of this two-band model to real systems , we compare simulation results obtained with the effective-mass wave-match ing theory and a single full-band model, which accounts for long-range inte ractions. A reasonable agreement on a wide range of incident energies is de monstrated for a GaAs-Al0.3Ga0.7As resonant tunneling diode (RTD) using a n oneffective-mass correction and a coupling factor of 0.999. An improved fit is further obtained by relaxing the backward interband coupling to zero. T he two-band model and the interface wave-matching procedure developed provi des a simple yet realistic approach to account for both noneffective-mass e ffects and the coupling between the Gamma and X or L valleys in the calcula tion of the transmission and reflection coefficients of RTD devices. Finall y, the impact of interface roughness scattering in the presence of Gamma-X coupling is studied and both the destruction and creation of antiresonant s tructures are observed. [S0163-1829(98)04744-4].