Photoconductivity of a strained InAs/InP superlattice in the 1.0-1.5 mu m region

The authors studied the first device structures in the compressive strain limit of the In(Ga)As/InP system. Strong excitonic transitions were observed in the photocurrent spectrum between 1.1 and 1.5 mu m. The hh1 to e1 transition showed a large Stark shift for such narrow wells (15 AA). A relatively simple model accurately predicted both allowed and forbidden heavy hole transitions for the strained, five-monolayer wells. However, the separation of the lh1 to e1 and hh1 to e1 transitions suggests either some relaxation of the strain or a degree of alloying. A structure containing this number of highly strained narrow wells places severe demands on the growth. The results obtained suggest that one of these constraints needs to be relaxed to obtain uniform, pseudomorphic MQWs (multiquantum wells). Nevertheless the strength of the excitonic transitions and magnitude of the Stark shift are encouraging for the fabrication of MQW detectors and modulators in the InGaAs/InP system using intermediate levels of strain and somewhat thicker wells.<>