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WOS: 000187286000001, We have theoretically investigated the intersubband transition for different doping concentrations and thickness in Si delta-doped GaAs with an applied electric field. The electronic properties such as the delta-potential profile and the subband energy have been calculated by solving the Schrodinger and Poisson equations self-consistently. We show an abrupt drop of the energy differences and the absorption peaks whenever the external electric field reaches a certain value. We can say that the appearance of a second quantum well in the effective potential dependent on the applied electric field creates a rapid change in the subband energies. This critical electric field value changes as dependent on the donor concentration and thickness. Thus, we conclude that the intersubband optical absorption is very sensitive to the donor distribution and thickness as dependent on the applied electric field. This changing in the intersubband transition gives a new degree of freedom in regions of interest semiconductor device applications.

For a uniform distribution we have theoretically studied the subband structure of p -type δ -doped GaAs inserted into a quantum well at T = 0 K. We will investigate the influence of the δ -doping concentration and the layer thickness. The electronic properties such as the depth of confining potential, the density profile, the Fermi level, the subband energies and the subband populations have been calculated by solving the Schrodinger and Poisson equations self consistently. In this study, we have seen that the heavy-hole subbands contain many more energy states than the light-hole ones, the population of the heavy-hole levels represent approximately 91% of all the carriers.

WOS: 000223511800011, For different applied electric fields the intersubband transitions of double Si delta-doped GaAs structures are theoretically investigated for a uniform donor distribution. The electronic structure has been calculated by solving the Schrodinger and Poisson equations self-consistently. It is found that the changes of the confining potential, the subband energies and intersubband optical absorption are quite sensitive to the applied electric field. Different from the single delta-doped structure, we have seen the abrupt changing of the subband energies and the absorption coefficient whenever the applied electric field reaches two certain values. While for the (1-2) intersubband transition, the intersubband absorption spectrum shows blueshifts up to the first critical electric field value, this spectrum shows redshifts up to the second critical electric field value and shows blueshifts for higher electric fields than the second critical field values. This behavior in the intersubband transitions for different electric fields can be used in some infrared optical device applications based on the intersubband transitions of electrons. (C) 2004 Elsevier Ltd. All rights reserved.

The results of the study of a novel monolithic wavelength converter / amplifier which can be timed, with the application of an external field are presented. The tuning range is Dl=300 Å about the operation wavelength, 1= 8400. The proposed device is a modified version of the HELLISH-1 (Hot Electron Light Emitting and Lasing Semiconductor Heterojunction) device1,2. It consists of a graded Ga1−xAlxAs quantum well (0< x< 0.15) placed on the n side of the depletion region, of a Ga0.7Al0.3As p-n junction, as shown in figure 1. As a result of the built-in field coupled with the grading the quantum well looks as if it were an isolated square well in zero field. Forward biasing the junction reduces the built-in field, thus the field associated with the grading becomes effective as shown in figure 2. The tuning of the operation wavelength is based on the Quantum Confined Stark Effect and is achieved during the forward biasing of the device. The wavelength as a function of the forward bias is shown in figure 3. Forward biasing the junction (electrical pumping) results in an enhanced conversion efficiency.