Vertical Transport Properties of Photogenerated Carrier in InGaAs/GaAs Strained Multiple Quantum Wells

We report on the carrier transport properties of a GaAs p-i-n structure including In x Ga1- x As/GaAs (x=0-0.15) strained multiple quantum wells (MQWs). Photocurrent measurements at room temperature showed that the spectral response extended to lower energies with increasing In content, and the quantum efficiency (ratio of the number of photogenerated carriers contributing photocurrent to the number of absorbed photons) was almost unity even when the well depth was several times greater than the thermal energy k T at room temperature. This is consistent with the calculation of the time for carriers to escape from the InGaAs/GaAs single quantum well. The calculation result also shows that applying a high electric field increases the photocurrent gain in MQW diodes.