Scaling the brightness (spatial coherence) along with output power has been a long-standing problem for semiconductor lasers. The difficulty arises due to complex spatiotemporal modal filamentation associated with light-matter interaction in the non-linear semiconductor lasing medium. This work presents a detailed study of spatiotemporal dynamics in wide aperture semiconductor lasers with the motivation of the identifying factors limiting brightness scaling in the high power regime thereby finding routes to scale the brightness using the unique properties of quantum confined active regions. In this view an opto-electro-thermal model is developed within the Maxwell-Bloch formalism with the capability of describing, frequency, carrier and temperature dependent semiconductor gain and dispersion. The model captures the essential spatiotemporal dynamics in both the thermal and non-thermal regimes and for both homogenous and inhomogeneous broadening in the semiconductor lasing medium. First a steady-state electro-thermal model is developed to simulate the current and heat spreading in the device. Finite element technique (FEM) based simulations are compared with experimental temperature maps obtained from micro-thermographic analysis producing an excellent match resulting in the first concerted study of bulk thermal properties of broad area quantum dot lasers. The thermal model is then used in conjunction with the Maxwell-Bloch based opto-electro-thermal model to obtain pump-dependent modal intensity structure and spatial frequency spectral characteristics. Effect of both homogeneous and inhomogeneous gain broadening is analysed in both the thermal and non-thermal regimes. It is shown via linear stability analysis and high resolution FEM simulations that presence of inhomogeneous gain broadening leads to improved spatial coherence and suppressed filamentation in both thermal and non-thermal regimes. A novel technique based on decoupling of lateral travelling waves corresponding to higher order spatial modes via index-anti-guiding is also described leading to a complete suppression of filamentary modal behaviour. Preliminary experimental results are presented validating the theoretical prediction.