DLTS study of Be-DOPED p-type AlGaAs/GaAs MBE layers

Deep-level transient spectroscopy method was applied to study deep hole traps in p-type Al$\text{}_{0.5}$Ga$\text{}_{0.5}$As grown on GaAs semi-insulating substrate by MBE. Five hole traps labelled by us as H0 to H4 were found. For the traps H1, H3 and H4 thermal activation energies obtained from Arrhenius plots were equal to: E$\text{}_{H1}$=0.15 eV, E$\text{}_{H3}$=0.4 eV, and E$\text{}_{H4}$=0.46 eV. Hole emission from the trap H2 was electric field dependent with the thermal activation energy extrapolated to zero-field equal to 0.37 eV. Capture cross-sections for the traps H1 and H4 were thermally activated with energetic barriers 0.04 eV (for H1) and 0.18 eV (for H4)

Raman spectroscopy of CdTe/ZnTe quantum dot structures

Semiconductor low-dimensional structures of CdTe quantum dots (QDs) embedded in ZnTe matrix have been investigated by micro-Raman spectroscopy. A reference ZnTe sample (without dots) was also studied for comparison. Both samples were grown by a molecular beam epitaxy technique on the p-type GaAs substrate. The Raman measurements have been performed at room temperature. The samples were excited by an Ar2+ laser of 514.5 nm wavelength. The Raman spectra have been recorded for different acquisition parameters of the measurement. For the reference and QD sample localized longitudinal (LO) phonons of 210 cm–1 wavenumber associated with the ZnTe layer are observed. In the case of QD sample another broadband corresponding to the LO CdTe phonon related to the QD-layer appears at a wavenumber of 160 cm–1. Such behaviour does not exhibit the Raman spectra of the reference sample. Thus the Raman measurements confirm the presence of CdTe layer of quantum dots in the investigated material. Additionally, Raman spectra for both samples exhibit tellurium-related peaks at wavenumbers around 120 cm–1 and 140 cm–1, significantly increasing with laser time exposure. It is shown that the peaks are associated with the formation of Te aggregates on the ZnTe surface due to the laser damage in the ZnTe layer

Thermally stimulated current in high resistivity Cd0.85Mn0.15Te doped with Indium.

Charge carrier traps in Cd(0,85)Mn(0,15)Te doped with indium were studied using thermally stimulated current measurements. The investigations were performed in temperatures ranging from 100 to 300 K. Four peaks in the current spectrum were identified. From the initial rise method and the best fit of the spectrum to the theoretical model, the activation energies and the relaxation parameters for the corresponding traps were determined

Capacitance-Voltage Studies of Ti/p-ZnTe Schottky Barrier Structures Containing CdTe Quantum Dots

In this paper the electronic states of self-organized CdTe quantum dots embedded in ZnTe matrix are studied by means of capacitance-voltage (C-V) characteristics within the temperature range of 180-300 K. A reference diode of the same layer structure but without quantum dots is studied also for comparison. The C-V characteristics measured for the reference diode exhibit bulk behaviour in contrast to the quantum dots sample for which a characteristic step corresponding to discharging of quantum dots is clearly visible within broad range of temperatures. A quasistatic model based on the self-consistent solution of the Poisson equations is used to simulate the capacitance. By comparison the calculated C-V curve with experimental curve the apparent thermal activation energy for hole emission from the quantum dots to the ZnTe matrix is found to be equal to (0.12 ± 0.03) eV