Abstract

Previously, in undoped and doped bulk GaAs with donor and acceptor densities >6 × 10¹⁵ cm⁻³, the maximum amount of blueshift of the donor-acceptor pair (DAP) transition peak observed is only ~ 3 meV.¹ For the first time, to the best of our knowledge, we have observed anomalously large blueshift of the DAP transition peak (~11 meV) in compensation-doped asymmetric-coupled quantum wells (QWs). Our sample was growt, by MBE on a semi-insulating GaAs substrate. The epitaxial layers consist of 20 periods, each of which is composed of two GaAs QWs with widths of 50 and 65 Å, respectively, coupled by a 35-Å Al_0.35Ga_0.65As barrier. The adjacent periods were isolated from each other by 150-Å Al_0.35Ga_0.65As barriers. Each 65-Å GaAs well was compensation doped by Be as acceptors and Si as donors, with densities of 3 × 10¹⁷ cm⁻³, A typical photoluminescence excitation (PLE) spectrum for our sample at 4 K is shown in Jig, 1 (with each peak assigned based on our calculations. A PL spectrum is also plotted in Fig. 1. The high-energy PL peak at ~7790 Å corresponds to excitonic recombination. The broad, low-energy emission peak corresponds to the DAP transition. In Fig. 2, we plotted normal-ized PL spectra for some selected pump intensities. We fitted each PL spectrum by two Gaussian line shapes corresponding to the excitonic and DAP emission peaks. As a result, there is a continuous blueshift of the DAP transition energy as large as ~11 meV when the laser intensity increases from 0.54 to 423 W/cm² (Fig. 3). This is the first observation of the blueshift of the DAP transition energy with such a large magnitude in compensation-doped QWs. The photon emitted in a DAP transition has the energy

© 1998 Optical Society of America