Modeling and Performance Analysis of GaSb-Based Mid-infrared Vertical Cavity Surface Emitting Laser

Abstract

Strain-dependent and crystal orientation-dependent optical properties and output optical power-input current characteristics are numerically studied for GalnSb/GalnAlSb mid-infrared quantum well vertical cavity surface emitting laser (VCSEL). At first physical model of the VCSEL is proposed and then mathematical formulations is developed taking into account of strain, change in crystal orientation and piezoelectric field. The results obtained from the model are confirmed with the published results. To investigate the performances of the proposed VCSEL. wave functions. energy dispersion profiles, and momentum matrix elements are determined by Schrodinger equation using finite dilièrence method. The results are calculated for a compressively strained quantum well in which strain is varied from 0.6% to 1.52% with the change in crystal orientation (001), (111), (110), (113) and (131). It is tbund that wave function confnenient. energy separation between different hands and subhands. and magnitude of momentum matrix elements are strongly dependent on strain. change in crystal orientation and piezoelectric fieId. The injection carrier density-dependent optical and differential gains are calculated. Typical optical gains are found to he 3115. 3080. 2790. 341 5. and 2940 cm in (001 ), (110), (111), (113). and (131) crystal orientations, respectively when the injection carrier density is 3,5x 1018 cm-3. Further, the maximum differential gain is evaluated 2.78x 1018cm-1 (113) orientation (or the injection carrier density 3.0x I 0IXcm-3. Ihe results obtained in the present stud• indicate that the peak emission wavelength can he tuned from 2.4 µm to 2.25 µm by changing crystal orientation from (110)10 (111) in the well and harrier materials. It is also found that the influence of piezoelectric effect is not so remarkable on the optical gain and shift in peal emission wavelength for the proposed VCSLL. To understand the output characteristics, the proposed VCSEL. model is converted into PSPICE equivalent circuit. The results obtained from PSPICE simulation demonstrate that the maximum output power and the minimum threshold current are associated with the crystal orientation and the ii umber of quantum wells. The highest optical power and lower threshold current are obtained hen the crystal orientation is (113) and number of quantum well is three. Furthermore, design of distributed Bragg reflector indicates 30 and 38 pairs of alternating layer of AlAs0.09 Sb0.91 and GaSb are used in top and bottom mirror in order to obtain reflectivity 99. 13% and 99.8% reflectivity.