Dependence of output emission wavelength and LD performance on barriers material and thickness

The output emission wavelength of MQW LDs depends on several structural and operating parameters such as the number of QWs, QW and barrier thickness, and material compositions which constitute the active region, operating current, and others. However, output emission wavelength mostly depends on the active region parameters like the thickness and In composition in wells and barriers. In this paper, effect of barriers material and thickness on the performance characteristics of deep violet InGaN DQW LDs were numerically studied. The simulation results demonstrate that output emission wavelength of a particular InGaN LD at different In compositions in the QWs (0.08 to 0.10) and barriers (0.0 (GaN), 0.01, and 0.02) is limited between 388 nm and 398 nm when the In mole fraction of the barriers is 0.0 (GaN). Likewise, output emission wavelength is limited between 391.7 nm and 421.0 nm, and 394.2 nm and 428.2 nm when the In mole fraction of the barriers is 0.01 (In0.01Ga0.99N) and 0.02 (In0.02Ga0.98N), respectively. Furthermore, the results indicated that by increasing barrier thickness, slope efficiency, output power, and DQE decrease, while threshold current increases. Increasing barrier thickness increased strain and piezoelectric fields in wells, thus resulted in an increasing electric field in the active region which helped increase nonradiative recombination and decrease radiative recombination in wells. The results also showed that optical characteristics decline with decreasing barrier thickness less than the critical thickness. Induced quantum-confined Stark effect (QCSE) in this situation resulting from the piezoelectric effect causes threshold current to increase, and output power, slope efficiency, and DQE to decrease.