Optimization of InGaAsP–InP tensile strained multiple quantum-well structures emitting at 1.34 µm

A systematic investigation has been undertaken on the growth, characterization and performance of tensile-strained multiple-quantum-well (MQW) lasers emitting at 1.34 mum. Two photoluminescence peaks corresponding to n = 1 electron-light hole (E1-LH1) and n = 1 electron-heavy hole (E1-HH1) transitions are clearly observed in MQW structures. The improvements of tensile strained MQW lasers such as the internal quantum efficiency, internal loss and threshold current are attributed to the increased energy separation between LH1 and HH1 when the tensile strain and well width are larger. The relatively thick barrier layer is required to mitigate the strain relaxation between the quantum wells. The degradation of device performance by the excessive barrier height could be attributed to the exacerbated spatial non-uniformity of the carrier distribution in the valence band. The optimized tensile strained MQW lasers with 300 mum cavity length and ridge waveguide (RWG) structure exhibit a lower threshold current of 13 mA and a higher external differential efficiency per facet of 0.29 mWmA(-1) at 25 degreesC.