Articles you may be interested inCalculation of metamorphic two-dimensional quantum energy system: Application to wetting layer states in InAs/InGaAs metamorphic quantum dot nanostructures Single quantum dot emission at telecom wavelengths from metamorphic InAs/InGaAs nanostructures grown on GaAs substrates Appl. Phys. Lett. 98, 173112 (2011); 10.1063/1.3584132 Properties of wetting layer states in low density InAs quantum dot nanostructures emitting at 1.3 μ m : Effects of InGaAs cappingWe present the study of optical and photoelectric properties of InAs quantum dots (QDs) grown on a metamorphic In 0.15 Ga 0.85 As buffer layer: such nanostructures show efficient light emission in the telecom window at 1.3 lm (0.95 eV) at room temperature. We prepared a sample with vertical geometry of contacts isolated from the GaAs substrate. The structure is found to be photosensitive in the spectral range above 0.9 eV at room temperature, showing distinctive features in the photovoltage and photocurrent spectra attributed to QDs, InAs wetting layer, and In 0.15 Ga 0.85 As metamorphic buffer, while a drop in the photoelectric signal above 1.36 eV is related to the GaAs layer. No effect of defect centers on the photoelectrical properties is found, although they are observed in the absorption spectrum. We conclude that metamorphic QDs have a low amount of interface-related defects close to the optically active region and charge carriers can be effectively collected into InAs QDs. V C 2015 AIP Publishing LLC. [http://dx.

Photoelectric properties of laterally correlated multilayer InGaAs/GaAs quantum dots (QDs) heterostructures are studied. The response of the photocurrent to increasing excitation intensity is found to be nonlinear and varying with excitation energy. The structures are photosensitive in a wide range of photon energies above 0.6 eV. The spectral dependence of the photoconductivity (PC) is caused by strong interaction between the bulk GaAs and the lower energy states of the wetting layer, the QDs, as well as the defect states in the GaAs band gap. In particular, a mechanism for the participation of deep electron trap levels in the photocurrent is clarified. These structures also demonstrate a high sensitivity of up to 10 A/W at low excitation intensities. However, at higher excitation intensities, the sensitivity reduces exhibiting a strong spectral dependence at the same time. The observed sublinear PC dependence on excitation power results from a direct electron-hole recombination both in the QDs and in GaAs host. The solution of rate equations included the contributions of QD ground and exited states, bulk GaAs states and the states of defects within the GaAs bandgap describes well the experimental data.

The surface functional layers of commercial detectorgrade CdTe crystals are characterized after different surface treatments such as chemical polishing etching in bromine-containing solutions and laser annealing with nanosecond pulses of the second harmonic of a YAG:Nd laser. The effects of etching and laser irradiation with energy density near the melting threshold of CdTe on the optical properties of the CdTe crystal surface are studied using ellipsometry and photoluminescence (PL). The samples after storage in air are also investigated. The intrinsic emission band at 1.58 eV and broad dopant band peaked at 1.45 eV are observed in the PL spectra excited by a semiconductor laser with wavelength of 405 nm at 80 K. The low energy band is associated with carrier recombination at structural defects in the surface layer. The redistribution of the PL band intensities after chemical polishing is found and it is attributed to transformation of the point defect structure and defect formation in the surface region of CdTe. The laser treatment essentially changes the surface state and structure of the surface layer that can be used for effective modification of characteristics of the functional layers of CdTe crystals particularly band bending before formation of electrical contacts.

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