CdZnTe Quantum Research Articles

Hydrogen passivation of nitrogen acceptors confined in CdZnTe quantum well structures

The deactivation of nitrogen acceptors confined in Cd0.96Zn0.04Te/Cd0.86Zn0.14Te quantum well structures by hydrogen (deuterium) have been investigated by optical spectroscopy. Hydrogen (deuterium) was incorporated into the samples by annealing them in an atmosphere of hydrogen and cadmium. The annealing temperature and annealing time were varied to determine the optimum condition at which the maximum passivation is achieved without causing structural degradation. The emissions related to nitrogen acceptors were monitored in low-temperature photoluminescence measurements in order to deduce the passivation effect. The results indicate that hydrogen can effectively neutralize the nitrogen acceptors in cadmium zinc telluride quantum well structures. It is estimated that as much as 90% of the nitrogen acceptors can be passivated by this method.

Are Quantum Wires with Strain-Induced Lateral Confinement Relaxed or not?

The optical transition energy in wires made from a GaAs/AlGaAs quantum well grown over an InGaAs/GaAs superlattice strained layer (III–V strained wires) has been calculated, taking into account the Γ8 symmetry of the valence band. We show that the experimental results in such a structure cannot be explained using a current model. A model assuming no relaxation at all, which accounts for the experimental results in the case of CdTe–CdZnTe quantum wires, is inadequate as well as the model previously used in the case of III–V strained wires, where the superlattice alone defines the strain in the wire. We then conclude that a partial, but not total, relaxation arises in these III–V strained wires. A relaxation theory has yet to be elaborated in quantum wires in which the lateral confinement is induced by strain.

Nitrogen acceptors confined in CdZnTe quantum well structures

Nitrogen acceptors confined in a CdZnTe single quantum well, grown by molecular beam epitaxy, are investigated by different optical methods. The transitions related to nitrogen acceptors confined in the well are observed in the doping range between 1017 and 1018/cm3. The temperature and excitation intensity dependence of the nitrogen-related transitions in photoluminescence spectra indicates that these transitions correspond to the nitrogen acceptor bound excitons and to free electron to neutral nitrogen acceptor recombination. The binding energy of nitrogen acceptors confined in an 130-Å-wide Cd0.96Zn0.04Te/Cd0.86Zn0.12Te structure is deduced to be 51.7±0.5 meV from this study.

Donor activation efficiency and doping profile quality in In-doped CdTe and CdZnTe quantum structures

In-doping of CdTe and Cd 1−x Zn x Te ( x < 20%) layers and quantum structures is performed during molecular beam epitaxy with a Cd overpressure. The In flux is determined as a function of the cell temperature. The role of the Cd overpressure in the activation efficiency is studied. Carrier mobilities of up to 5300 cm 2 V −1 s −1 are observed at light doping levels. In migration and formation of In-related compounds are studied by X-ray photoelectron spectroscopy. The doping profile quality is studied by secondary ion mass spectroscopy: efficient, well localized doping is achieved for low growth temperatures (200–220°C) and low sheet densities (about 10 11 cm −2); otherwise marked migration of the dopant is observed.