Resonant tunneling of holes in the multiband effective-mass approximation

EFFECT OF REMOTE BAND COUPLING ON NET RECOMBINATION CURRENT IN TYPE-II HETEROSTRUCTURES

Exact analytical expressions for the eigenvalues and eigenvectors of the six-band k · p matrix Hamiltonian for narrow-gap III–V semiconductors are used to derive an analytical expression for the transmission coefficient T in type-II heterojunctions. The remote band coupling is included via the two Luttinger-type parameters, γ1 and [Formula: see text]. The expression for T contains two separate contributions: one from electron to light-hole tunneling and the other from electron to heavy-hole tunneling. Using the expression for T, the net recombination current density J is defined and evaluated for the specific case of an InAs/GaSb heterojunction. Ohmic behavior is observed in J for small applied voltages V approximately in the range -0.15 to 0.075 eV. Outside of this range, J changes nonlinearly with respect to changes in V. Comparison of the heavy-hole and light-hole contributions to J shows that the heavy-hole contribution increases J by approximately 10% at room temperature. The results for the InAs/GaSb heterojunction are in qualitative agreement with recent experimental observations.

Resonant enhancement of tunneling magnetoresistance in double-barrier magnetic heterostructures

We show that spin-dependent resonant tunneling can dramatically enhance tunneling magnetoresistance. We consider double-barrier structures comprising a semiconductor quantum well between two insulating barriers and two ferromagnetic electrodes. By tuning the width of the quantum well, the lowest resonant level can be moved into the energy interval where the density of states for minority spins is zero. This leads to a great enhancement of the magnetoresistance, which exhibits a strong maximum as a function of the quantum well width. We demonstrate that magnetoresistance exceeding 800% is achievable in GaMnAs/AlAs/GaAs/AlAs/GaMnAs double-barrier structures.

Dominance of Fermi-surface holes in p-type tunneling

In-plane uniaxial stress is used to tune continuously the mixing between the heavy-hole (HH) and light-hole (LH) states in a p-type double-barrier structure. The LH1 and HH2 resonant tunneling peaks shift at almost the same rate with stress, in contrast to the corresponding exciton peaks observed by photoreflectance, which exhibit a strong Fano-related anticrossing. Comparison between the observed shifts and a four-band k x p calculation of the state energies in the well provides the first experimental proof that the flow of holes through off-zone center states dominates the resonant tunneling current in p-type structures.