INTRASUBBAND PLASMONS IN DELTA-DOPED INGAAS SINGLE QUANTUM-WELLS

Polarization-resolved infrared techniques have been applied to study t he optical properties of the quasi-two-dimensional electron gas in dop ed InGaAs quantum wells and to show that inter- and intrasubband proce sses can be distinguished by their polarization sensitivity. Distinct excitations of inter- and intrasubband transitions at the GAMMA(q = k = 0) point in delta-doped narrow InGaAs/AlAs single quantum wells were resolved through the use of quantum well structures designed to incre ase their energy difference and thus diminish the coupling between the se two processes. Longitudinal q(z) intrasubband plasmons were observe d at 1550 cm-1 and were excited by transverse-magnetic (TM) polarized light; the intersubband transitions occurred at around 4000 cm-1 and w ere both transverse-electric (TE) and TM polarization active.