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Photoluminescence measurements at different temperatures have been performed to investigate the optical response of a two-dimensional electron gas in n-type wide parabolic quantum wells. A series of samples with different well widths in the range of 1000–3000 Å was analyzed. Many-body effects, usually observed in the recombination process of a two-dimensional electron gas, appear as a strong enhancement in the photoluminescence spectra at the Fermi level at low temperature only in the thinnest parabolic quantum wells. The suppression of the many-body effect in the thicker quantum wells was attributed to the decrease of the overlap between the wavefunctions of the photocreated holes and the two-dimensional electrons belonging to the highest occupied electron subband. [ABSTRACT FROM AUTHOR]

The optical properties of n- and p-type, modulation- and delta-doped Al[sub 0.35]Ga[sub 0.65]As-GaAs single heterojunctions (SHs) have been studied by means of low-temperature photoluminescence measurement and self-consistent calculation. A very strong, broad, and asymmetric H-band emission was observed only in p-type delta-doped SH. When the optical excitation intensity increases by two orders of magnitude a redshift as large as 27 meV is observed in the H-band emission energy. The large redshift observed is attributed to both inefficiency of screening in the two-dimensional-hole gas and effective band-gap renormalization. It was also observed that the H-band emission strongly depends upon the doping type (n or p type) and doping profile (modulation doping or delta doping). [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) spectroscopy and atomic-force microscopy (AFM) were used to investigate the size evolution of InAs quantum dots on GaAs(001) as a function of the amount of InAs material. Different families of islands were observed in the AFM images and unambiguously identified in the PL spectra, together with the signal of the wetting layer. PL measurements carried out at low and intermediate temperatures showed a thermal carrier redistribution among dots belonging to different families. The physical origin of this behavior is explained in terms of the different temperature dependence of the carrier-capture rate into the quantum dots. At high temperatures, an enhancement of the total PL-integrated intensity of the largest-sized quantum dots was attributed to the increase of diffusivity of the photogenerated carriers inside the wetting layer. [ABSTRACT FROM AUTHOR]