Bound exciton luminescence in GaP:Cu,O

Luminescence from Cu,O-diffused high-ohmic p-type GaP crystals exhibits hitherto unobserved complexity in the red spectral region (1.6−1.9 eV). The present investigation concerns the features of three different emission series, denoted by C, E₁ and E₂, simultaneously present in these crystals. From detailed measurements of emission and excitation spectra at different temperatures the properties of any of these emissions could be studied separately. The low-temperature spectra for the two line emission series E₁ (1.78−1.72 eV) and E₂ (1.67−1.62 eV) show strong resemblances to well-known properties of isoelectronic complexes such as, for example, Cd,O in GaP. The featureless broad C emission (1.81 eV) is probably of a similar physical origin as E₁ and E₂, so that all three emissions are believed to originate from excitons bound to different complexes involving Cu and possibly O. Further work to determine the chemical nature of these defects is suggested.     

Mie resonances, infrared emission, and the band gap of InN

Mie resonances due to scattering or absorption of light in InN-containing clusters of metallic In may have been erroneously interpreted as the infrared band gap absorption in tens of papers. Here we show by direct thermally detected optical absorption measurements that the true band gap of InN is markedly wider than the currently accepted 0.7 eV. Microcathodoluminescence studies complemented by the imaging of metallic In have shown that bright infrared emission at 0.7-0.8 eV arises in a close vicinity of In inclusions and is likely associated with surface states at the metal/InN interfaces.     

Properties of Si δ-layers embedded in GaAs

An ultrathin, a few monolayers (MLs) thick Si δ-layer, has been embedded in GaAs. The Si δ-layer properties have been electrically and structurally characterized. A conductivity transition has been observed, when going from free carrier transport in thin (1 ML) ordered δ-layers to the disordered conditions for Si δ-layers thicker than 4 MLs. Two novel emission bands are observed in photoluminescence (PL) for Si δ-layers in the width range 1–4 MLs, but solely at below bandgap excitation. The pronounced 2D properties of these δ-layers have been clearly demonstrated by an observed blue shift of the PL characterization as the thickness of the Si δ-layer is reduced. The so-derived results on the transition energies and the electronic structure are in good agreement with theoretical predictions obtained by a self-consistent approach.     

Variations in the confining potential of doped AlGaAs/GaAs quantum wells with the photon energy of excitation

A series of doped GaAs/AlGaAs single quantum well samples has been investigated using photoluminescence (PL) and PL excitation (PLE) spectroscopy. The samples are of 100 Å well width and are doped in the central 50 Å with Si in the range 5×10⁸ to 2×10¹² cm⁻². A strong dependence of the optical spectra on the photon energy of excitation is observed. This dependence is interpreted in terms of a charge transfer process between the AlGaAs barrier and the quantum well (QW), which determines the charge and potential distribution in the QW.