Separate confinement heterostructure design for InGaAlAs/InP multiple-quantum-well lasers: critical analysis and proposal of novel design

Abstract

A thorough analysis on the separate confinement heterostructure (SCH) designed for 1.5-μm InGaAlAs/InP multiplequantum- well (MQW) lasers is presented. Simulation results show that the enhancement rates of the threshold current and the slope efficiency of graded-index SCH (GRINSCH) drop with the increasing number of graded layers. Hence, requirement on truly graded structure may be relieved, which eases the growth process and reduces the cost. The thickness of the GRINSCH has a profound impact on the laser's performance, whereby over 25 mA reduction in threshold current was deducible by optimizing this design parameter alone. The grading energy range of the GRINSCH is found to effectively reduce the carrier leakage at elevated temperature, resulting in improved threshold current's sensitivity to the temperature. However, the increased GRINSCH energy barrier may also bring detrimental effect to the slope efficiency. To overcome this problem, a non-symmetrical SCH (NS-SCH) structure with reduced n-SCH energy barrier is proposed. Simulation results show that laser structure with NS-SCH design has better light-current performance than the laser structure with electron stopper layer. The laser structure with NS-SCH exhibits 20% decrease in threshold current and 43% increase of maximum output power as compared to those of the reference laser structure.