Phase Space Absorption Quenching in a Single InGaAs Quantum Well FET

By changing the gate voltage of a single QW channel FET of InGaAs, we can vary the density of carriers n in this channel, originating from modulation doping of one of the InAlAs barriers. The n-dependent variations of the absorption spectrum of the QW are measured by sending a light beam fromthe 330InP substrate through the QW and reflecting it back from the metal gate. The nz = 1 resonance is modified predominantly by phase-space filling. This effect is absent for the nz = 2 and 3 states, which then show the band gap renormalization with n.