Asymmetric Resonance-tunneling Structures Research Articles

Optical and structural studies of dual wavelength InGaN/GaN tunnel-injection light emitting diodes grown by metalorganic chemical vapor deposition

InGaN/GaN multiple quantum well light emitting diodes with charge asymmetric resonance tunneling structure, which can emit dual color lights of blue/green or blue/yellow, were grown on sapphire by metalorganic chemical vapor deposition. Their optical and structural properties are studied by high-resolution X-ray diffraction, high-resolution transmission electron microscopy, temperature-dependent photoluminescence (PL) and photoluminescence excitation (PLE). PL peak shifts and PLE features are found to vary with the well-growth temperature. The luminescence mechanism is discussed in details, correlating to the In composition fluctuation, carrier localization and the quantum confined Stark effect.

Terahertz generation based on an optically pumped ballistic electron wave swing device

Terahertz (THz) signals can be generated by the periodic motion of ballistic electron bunches inside a quantum well cavity surrounded by two asymmetric resonant tunneling structure implemented in an InAlAs/InGaAs heterostructure. The electron bunches are produced in an adjacent active quantum well by optical excitation with a femtosecond laser pulse, and transferred into the cavity by resonant tunneling. The device contains also a superlattice that eliminates the electrons, which exit the cavity in the direction of the active quantum well. In consequence, the device output consists of a train of ultrashort pulses, of less than 100 fs, which preserve their coherence. Electrical signals up to few tens of THz can be obtained, depending on the resonant filter or antenna placed at the end of the device.

High brightness green light emitting diodes with charge asymmetric resonance tunneling structure

In this work, we have applied the so called charge asymmetric resonance tunneling (CART) structure to nitride-based green light emitting diode (LED). From our CART LED, we observed an abrupt turn-on voltage near 2.2 V, and the forward voltage is around 3.2 V at 20 mA injection current. At 20 mA, the output power, and external quantum efficiency of the CART LED are about 4 mW, and 6.25%, respectively. The high brightness and efficiency green LED can be obtained by using the CART structure.

Spin-polarized electronic current in resonant tunneling heterostructures

The spin-dependent tunneling phenomenon in symmetric and asymmetric resonant semiconductor heterostructures is employed in a theoretical study to investigate the output tunnel current polarization at zero magnetic field. A simple model of the resonant tunneling structures and a simple one-electron band approximation with spin-orbit interaction are used in this work. It is shown that asymmetry in the electron distribution at the electrode regions provides spin-polarized tunnel current. An approach to optimize this spin-dependent effect is explored theoretically. In asymmetric resonant tunneling structures, we estimate theoretically that the polarization can reach 40% with a moderate applied electric field.

Monolithic integration of red, blue, and green lasers for smart projection displays

Abstract— Novel device structures integrating multiple‐output lasers emitting in red, green, and blue colors are proposed. Active layers emitting red (AlGaAs or InGaAlP), blue (ZnxCd1−xSe), and green (ZnyCd1−ySe) are shown to be integrated monolithically on GaAs substrates using conventional p‐n tunnel junctions and asymmetric resonant tunneling structures. Both edge‐ and surface‐emitting structures are described. Experimental characteristics of two red‐emitting Al0.16Ga0.84As‐Al0.45Ga0.55As‐GaAs lasers, integrated in tandem via a low‐voltage‐drop tunnel junction are presented, demonstrating the feasibility of monolithic integration. Blue‐green lasers are shown to operate at lower voltages using asymmetric resonant tunneling structures between p‐GaAs/p‐ZnSe layers. Integration of surface‐emitting lasers including folded‐cavity and Distributed Bragg Reflector (DBR) structures is also presented along with simulation of electrical and optical characteristics. An integrated pixel‐addressing methodology is described for smart projection displays.

Anomalous suppression of the probability of resonance interaction of electrons with an rf field in asymmetric double-barrier structures on account of plasma oscillations

An analytical self-consistent solution of the nonstationary Schrodinger and Poisson equations describing the resonance interaction of electrons with a radio-frequency (rf) field has been found for asymmetric resonance-tunneling structures with high, thin barriers. It is shown that plasma oscillations limit the probability of transitions between neighboring levels and suppress anomalously strongly transitions in which the level number changes by more than 1 (by tens and hundreds of times compared with transitions between neighboring levels).

Unusual behavior of the electron reflection coefficient of asymmetric double-barrier quantum structures in a finite-amplitude rf field

The time-dependent Schrodinger equation describing the resonance interaction of electrons with a radio-frequency (rf) field is solved for asymmetric resonance-tunneling structures with thin, high barriers. It is found that in a number of cases the resonance reflection coefficient of such structures decreases almost to zero as the amplitude of the rf field increases. The conditions under which the largest number of electrons incident on the structure (in a number of cases 100%) interacts efficiently with an rf field with frequency ω and pass into a neighboring resonance level, emitting or absorbing a quantum of energy ħω, are determined.

Influence of impurity scattering on the traversal time and current-voltage characteristics of resonant tunneling structures

The transmission line technique to solve the time independent Schrödinger equation is modified to include the effect of elastic scattering by introducing a scattering impedance Z s = 4 jV 0/ℏ. The method is applied to calculate the current-voltage and traversal time characteristics of double barrier resonant tunneling structures. The peak current density for a random distribution of scatterers in the quantum well decreases while it increases for scattering at a fixed location compared to its value in the absence of any scatterers. Traversal time decreases with applied bias and shows distinct dips at resonance. The traversal time through an asymmetric resonant tunneling structure is also investigated.