Analysis of the quantum confined stark effect in GaSb/AlGaSb multiple quantum wells

There has been much interest recently in the electric field dependence of the optical absorption in multiple quantum wells (MQWs). This phenomenon, known as the Quantum Confined Stark Effect (QCSE),[1] has many device applications, one of which is high-speed optical intensity modulators for fiber optic systems. Modulators were first demonstrated in the 0.8 µm wavelength region using GaAs/AlGaAs,[2] but more recently attention has shifted to InGaAs/InAlAs,[3] InGaAs/InP[4] [5] and GaSb/AlGaSb[6] material systems which operate near the optical fiber loss minimum at 1.55 µm. To understand these devices, Miller et al. developed a theory for the QCSE[1] that was in good agreement with their experimental data for GaAs/AlGaAs MQWs. The theory was also successfully applied to InGaAs/InP MQWs.[7] In this paper we extend that theory to GaSb/AlGaSb and compare it with our experimental data. Because of the sizable lattice mismatch of 0.65% between GaSb and AlSb, strain effects can become very important in GaSb/AlSb MQWs. We show that the use of AlGaSb barriers significantly reduces these effects.