Well width dependence of threshold in InGaN/AlGaN quantum well lasers

Summary form only given. Group-III nitride lasers are important because they emit at short wave-lengths, where there are many optoelectronic applications. As these lasers are in an early developmental stage, there is much interest in developing an understanding of physical mechanisms, expected device performance, and optimal laser configurations. One important question is the dependence of laser properties on quantum well configuration. For example, quantum confinement and epitaxial growth considerations tend to favor narrow quantum wells of width around 2 nm or less. However, experimental data seem to indicate that the laser threshold may be lower with wider wells. To determine if the above result is fundamental to the nitride-based lasers, we investigate the spontaneous emission contribution to the threshold current density. We use a many-body gain theory that gives a consistent account of the strong Coulomb effects in the nitride compounds, and has the important advantage of eliminating the dephasing rate as a free parameter. The latter makes the predictions of important quantities, such as peak gain and transparency carrier density, more precise.