Delta-doped quantum wire tunnel junction for highly concentrated solar cells

We propose a novel structure for tunnel junction based on delta-doped AlGaAs/GaAs quantum wires. Higher spatial confinement of quantum wires alongside the increased effective doping concentration in the delta-doped regions extremely increase the peak tunneling current and enhance the performance of tunnel junction. The proposed structure can be used as tunnel junction in the multijunction solar cells under the highest possible thermodynamically limited solar concentration.The combination of the quantum wire with the delta-doped structure can be of benefit to the solar cells' advantages including higher number of sub-bands and high degeneracy. Simulation results show a voltage drop of 40 mV due to the proposed tunnel junction used in a multijunction solar cell which presents an extremely low resistance to the achieved peak tunneling current.

Interlayer distance effects on absorption coefficient and refraction index change in p-type double-δ-doped GaAs quantum wells

In the framework of the Thomas–Fermi(TF) approach, a model for the p-type double-δ-doped(DDD) system in Ga As is presented. This model, unlike other works in the literature, takes into account that the Poisson equation associated with the system is nonlinear. The electronic structure is calculated for heavy and light holes. The changes in the electronic structure result of the distance d between the doped layers are studied. In particular, the relative absorption coefficient as well as the relative refractive index change is calculated as a function of the incident photon energy for heavy holes. The effect of the interlayer distance exhibits, in the absorption coefficient, a red shift of the peak position and a decrease in amplitude when the distance increases. In addition, the relative refractive index change node has a red shift as well as the interlayer distance increases. The calculations show that the effect of the separation between layers has a greater influence on the linear terms. These results are very important for theoretical calculations and engineering of optical and electronic devices based in δ-doped Ga As.

Nonlinear optical properties in n-type quadrupleδ-doped GaAs quantum wells

The effects of the interlayer distance on the nonlinear optical properties of n-type quadrupleδ-doped GaAs quantum well were theoretically investigated.Particularly,the absorption coefficient and the relative refraction index change were determined.In the effective mass approach and within the framework of the Thomas-Fermi theory,the Schrodinger equation was resolved.Thereby,the subband energy levels and their respective wave functions were calculated.The variations in the nonlinear optical properties were determined by using the density matrix solutions.The achieved results demonstrate that the interlayer distance causes optical red-shift on nonlinear optical properties.Therefore,it can be deduced that the suitably chosen interlayer distance can be used to tune optical properties within the infrared spectrum region in optoelectronic devices such as far-infrared photo-detectors,high-speed electronic-optical modulators,and infrared lasers.