Performance improvement of optoelectronic devices using group III Nitride based quantum dot

Quantum dot has become a subject of incredible interest in the field of semiconductor optoelectronic device design for the researchers due to some of their unique properties. Among the wide range of optoelectronic devices some important characteristics of solar cell and laser have been studied extensively. These two devices are chosen because of the importance of these optoelectronic semiconductor devices in the field of renewable energy and optical fiber communication respectively. Recently it has been acknowledged that the researchers are paying more and more attention to the group-III nitride based quantum dots. Therefore this research is devoted to investigate the performance improvement of solar cell and laser using InN based quantum dot in the active layer of the device structure. In this research work the performance improvement of both these devices have been achieved by changing the active layer material without affecting other structural parameters. The effect of lattice constant on band gap energy optimization of In𝑥Ga₁_𝑥N has been investigated initially. From the numerical analysis it has been found that In𝑥Ga₁_𝑥N offers a band gap energy ranging from 0.7eV - 3.5eV, which makes it a suitable material for solar cell to absorb a wide range of light energy. Furthermore, it has been demonstrated that In0.87Ga0.13N is capable of emitting light at the wavelength of 1.55μm, which offers the lowest attenuation for signal transmission through optical fiber. Therefore the result of initial investigation ascertains that In𝑥Ga₁_𝑥N can be a promising material for the fabrication of solar cell as well as laser. Then the temperature dependence of the band gap energy of semiconductor material was investigated using Varshni’s model and Bose–Einstein model. While analyzing the temperature dependence of band gap energy of GaN using these two models a major limitation of Bose–Einstein model has been identified and a modification of this model has been proposed to solve the problem of calculation of critical temperature. After that the absorption and emission phenomena, effect of operating time on the feed-back characteristics and the cavity length dependence of the loss and gain characteristics and photon life time of quantum dot laser were investigated. Furthermore the effect of temperature on the drift length and the diffusion length of the carriers have been investigated along with the open circuit voltage, short circuit current, output power of the solar cell. The numerical results obtained were compared with those obtained by using other conventional existing materials for both laser and solar cell. For laser obtained numerical results were compared with GaN and AlN quantum dot based laser and for solar cell, obtained results were compared with Si and Ge quantum dot based solar cell. Numerical results reveal that the laser characteristics have been improved drastically and the stability of solar cell characteristics has been increased significantly using InN quantum dot as the active layer material. Finally it can be concluded that InN quantum dot can be a promising material to fabricate the optoelectronic devices in the very near future.