Transition of carrier distribution from a strained to relaxed state in InGaAs/GaAs quantum well

This work investigates the transition of carrier distribution from the strained to the relaxed state in In_0.2Ga_0.8As/GaAs quantum well by measuring capacitance voltage and analyzing x-ray diffraction. According to those results, there is carrier confinement in the In_0.2Ga_0.8As quantum well with well thickness less than the critical thickness. Increasing the well thickness beyond the critical thickness leads to a significant carrier depletion around the quantum well. Double-crystal x-ray rocking curves reveal that when InGaAs well thickness increases beyond the critical thickness, the interference pattern disappears and relaxation begins to occur from near the bottom InGaAs/GaAs interface while the top interface still remains strained. Results obtained from the critical thickness determined from x-ray diffraction correspond to the transition of carrier distribution, illustrating that the capacitance-voltage measurement is a rather effective means of determining the critical thickness.