College of Education for Pure Science

Master Thesis Viva in the College of Education for Pure Science entitled ” Study and Analysis of The Optical and Spectral Properties of Arsenic-doped InP/GaAs Quantum Dot Semiconductor Lasers”The College of Education for Pure Science, University of Mosul, has done the Master Thesis Viva entitled ” Study and Analysis of The Optical and Spectral Properties of Arsenic-doped InP/GaAs Quantum Dot Semiconductor Lasers”,On Sunday, September 11, 2022, the College staff including the respected Dean of the College, Assistant Professor Dr. Qais Ismail Ibrahim, the Honorable Scientific Associate and Administrative Associate, the Honorable Head of the Department of Physics, and a number of the college’s teachers were attended the viva. The aim of this study, presented by the Master student Rafal Zuhair Bahnam in the Department of Physics, is to study and investigate the role of 20 % As doping to InP quantum dot (QD) laser. For that reason, two QD materials as a laser active region were prepared namely, InP and InAs0.2P0.8 QDs. Both of them were grown at the same conditions by standard MOVPE technique on the compatible structure. To study the laser performance 1mm cavity length lasers were prepared for both samples. Moreover, multi-section devices were prepared to measure the modal absorption spectra of the samples using segmented contact method. The simulation part in this study involves applying of the Gaussian distribution on the modal absorption to calculate the optical absorption cross section and the inhomogeneous broadening. Additionally, applying Lorentziandistribution on the laser emission spectra to study the linewidth broadening and carrier’s lifetime. The laser results shown that both samples displayed adequate performance over the wide range of temperatures ( -100 to 100 0C). The optical power – current (P-I) curves conformed lasing operation of both samples up to 100 0C. However, the As doped sample presented larger threshold current, for examples, at 200C the threshold current is approximately 187.8 mA for InP and 247.2 mA for InAsP. Moreover, the results of current –voltage (I-V) curves pointed out high electrical connections over the measured temperatures range for both samples. Additionally, the emission spectrum was shifted from around 716 nm to around 760 nm when As was added to InP. On the other hand, the simulation results showed, adding As to InP QD material increases the optical absorption cross section for the ground states (GS) by 0.836 x10-14 cm2.eV whereas, the excited state (ES) showed almost same value. Moreover, the inhomogeneous broadening for InAsP sample was doubled and became less well defined. Furthermore, the linewidth broadening of the lasing state increase by 1.1 meV and the e carrier lifetime reduces from 0.866 Ps to 0.222 Ps when As was doped. These results could make InAsP QD laser an attractive device in photo dynamic therapy application where longer wavelength laser is required. Moreover, the wider emission spectra be helpful in applications such as mode-locking, Q-switching and ultra-fast pulse generation. Finally, the results could also help the grower to control the growth conditions and the molecule fractions of the crystal to improve the spectra properties of the optoelectronics materials.The Viva committee was chaired by Asst. Prof. Dr. Erada A. Aldabagh/ Mosul University / College of Science , and the membership of Asst. Prof. Dr. Khalil I. Mohammad/ Kirkuk University / College of Education – Hawija, Lecturer Dr. Fathi M. Jasim, University of Mosul / College of Education for Pure Science, and under the supervision and membership of Asst. Prof. Dr. Ivan Bahnam Karomi, University of Mosul / College of Education for Pure Science.