Strained Layer Multiquantum Barriers with Improved Carrier Injection and Confinement

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Abstract
The effects of using strained layer superlattice in multiquantum barriers (MQBs) were analyzed with focus on InP-based materials and their application to strained layer multiquantum well lasers (SL-MQW LDs). Tensile strained barriers are shown to largely increase the effective barrier height of MQBs. A new barrier material, AlInP, which is 1–1.5% tensile strained on InP, is shown to have inherent advantages of large conduction band edge discontinuity ΔE c and low aluminum content compared to conventional AlInAs on InP. Those advantages are confirmed for strain-compensated MQB with tensile barrier/compressive well in terms of increasing the effective barrier height. Some disadvantages of the strain-compensated MQB are also pointed out; the increase in density of holes injected into the MQB region under lasing conditions and the high p-doping concentration required. To solve those problems, an improved method of carrier injection through minibands with gradually enhanced energy levels toward the MQW region is presented, which is shown to enable elimination of the carrier transport effect and to result in marked improvement in laser performances.