Deep-level defects in n-type GaAsBi alloys grown by molecular beam epitaxy at low temperature and their influence on optical properties

Deep-level defects in n-type GaAs1-x Bi x having 0 ≤ x ≤ 0.023 grown on GaAs by molecular beam epitaxy at substrate temperature of 378 °C have been injvestigated by deep level transient spectroscopy. The optical properties of the layers have been studied by contactless electroreflectance and photoluminescence. We find that incorporating Bi suppresses the formation of GaAs-like electron traps, thus reducing the total trap concentration in dilute GaAsBi layers by over two orders of magnitude compared to GaAs grown under the same conditions. In order to distinguish between Bi- and host-related traps and to identify their possible origin, we used the GaAsBi band gap diagram to correlate their activation energies in samples with different Bi contents. This approach was recently successfully applied for the identification of electron traps in n-type GaAs1-x N x and assumes that the activation energy of electron traps decreases with the Bi (or N)-related downward shift of the conduction band. On the basis of this diagram and under the support of recent theoretical calculations, at least two Bi-related traps were revealed and associated with Bi pair defects, i.e. (VGa+BiGa)(-/2-) and (AsGa+BiGa)(0/1-). In the present work it is shown that these defects also influence the photoluminescence properties of GaAsBi alloys

Effect of Co-60 gamma-ray irradiation on electrical properties of Ti/Au/GaAs1-xNx Schottky diodes

Current-voltage (I-V), capacitance-voltage-frequency (C-V-f) and conductance-voltage-frequency (G/ω-V-f) measurements at room temperature are used to study 50 kGy 60Co γ-ray electrical properties irradiation dependence of Ti/Au/GaAs1−xNx Schottky diodes with 0.2%; 0.4%; 0.8% and 1.2% nitrogen dilution. This γ-ray irradiation induces a permanent damage that has increased ideality factor and series resistance for all samples. It was accompanied by a decrease in Schottky barrier height with nitrogen content up to 0.4%N and remained constant thereafter. Radiation was also found to degrade the reverse leakage current. At high frequency (1 MHz), capacitance and conductance decreased after radiation due to a decrease in net doping concentration. Interface state density and series resistance were determined from C-V-f and G/ω-V-f characteristics using Hill-Coleman methods. Interface states density exponentially decreased with increasing frequency confirming the behavior of interface traps response to ac signal. Series resistance increases after irradiation is attributed to carrier's removal effect and mobility degradation. It has two peaks in the accumulation and inversion region for some diodes (0.4%N, 0.8%N). γ-ray irradiation produced traps levels and recombination centers that reduce relaxation time. An increase in %N content can impede irradiation damage with even some compensation when the percent of diluted nitrogen is high (1.2%N)

GaSbBi alloys and heterostructures: fabrication and properties

International audienceDilute bismuth (Bi) III-V alloys have recently attracted great attention, due to their properties of band-gap reduction and spin-orbit splitting. The incorporation of Bi into antimonide based III-V semiconductors is very attractive for the development of new optoelectronic devices working in the mid-infrared range (2-5 µm). However, due to its large size, Bi does not readily incorporate into III-V alloys and the epitaxy of III-V dilute bismides is thus very challenging. This book chapter presents the most recent developments in the epitaxy and characterization of GaSbBi alloys and heterostructures

DLTS Investigations of (Ga,In)(N,As)/GaAs Quantum Wells before and after Rapid Thermal Annealing

Deep level transient spectroscopy was used to investigate deep-level defects in (Ga,In)(N,As)/GaAs triple quantum well structures grown by atmospheric pressure metalorganic vapor phase epitaxy with different indium and nitrogen contents and annealed in rapid thermal annealing system. A combination of electron traps that disappear or remain on annealing and a new hole trap that appears on annealing were detected. The revealed electron traps were attributed to N-related complexes or GaAs host-related native point defects. Moreover, it was suggested that the new hole trap observed in the annealed GaAsN/GaAs triple quantum well structure together with the dominant electron trap can act as generation-recombination center responsible for the observed a very poor optical quality among all the investigated multi-quantum well structures

Misfit Dislocations Study in MOVPE Grown Lattice-Mismatched InGaAs/GaAs Heterostructures by Means of DLTS Technique

Two deep traps associated with lattice-mismatch induced defects in n-type In$\text{}_{0.042}$Ga$\text{}_{0.958}$As/GaAs heterostructures and three deep point traps were observed by means of DLTS method. In order to determine the overlapping DLTS-line peaks parameters precisely, high resolution Laplace DLTS studies werw performed. A simple procedure of distinguishing between point and extended defects in DLTS measurements was used

Investigation of deep levels in bulk GaN material grown by halide vapor phase epitaxy

Electron traps in thick free standing GaN grown by halide vapor phase epitaxy were characterized by deep level transient spectroscopy. The measurements revealed six electron traps with activation energy of 0.252 (E1), 0.53 (E2), 0.65 (E4), 0.69 (E3), 1.40 (E5), and 1.55 eV (E6), respectively. Among the observed levels, trap E6 has not been previously reported. The filling pulse method was employed to determine the temperature dependence of the capture cross section and to distinguish between point defects and extended defects. From these measurements, we have determined the capture cross section for level E1, E2, and E4 to 3.2 × 10−16 cm2, 2.2 × 10−17 cm2, and 1.9 × 10−17 cm2, respectively. All of the measured capture cross sections were temperature independent in the measured temperature range. From the electron capturing kinetic, we conclude that trap E1, E2, and E3 are associated with point defects. From the defect concentration profile obtained by double correlated deep level transient spectroscopy, we suggest that trap E4 and E6 are introduced by the polishing process.Funding Agencies|Swedish Research Science Council (VR)||Swedish Energy Agency||</p

STRUCTURAL CHARACTERIZATION OF DOPED THICK GaInNAs LAYERS ---AMBIGUITIES AND CHALLENGES

GaInNAs alloys are mostly used as an active part of light sources for long wavelength telecom applications. Beside this, these materials are used as thin quantum wells (QWs), and a need is to grow thick layers of such semiconductor alloys for photodetectors and photovoltaic cells applications. However, structural characterization of the GaInNAs layers is hindered by non-homogeneity of the In and N distributions along the layer. In this work the challenges of the structural characterization of doped thick GaInNAs layers grown by atmospheric pressure metalorganic vapour phase epitaxy (APMOVPE) will be presented

Bi-induced acceptor level responsible for partial compensation of native free electron density in InP1-xBix dilute bismide alloys

Deep level transient spectroscopy (DLTS) has been applied to study electron and hole traps in InPBi alloys with 2.2 and 2.4% Bi grown by molecular beam epitaxy. One donor-like trap with the activation energy of 0.45-0.47 eV and one acceptor-like trap with activation energy of 0.08 eV have been identified in DLTS measurements. For the reference sample (InP grown at the same temperature), the deep donor trap has also been observed, while the acceptor trap was not detected. According to the literature, the deep donor level found in InP(Bi) at 0.45-0.47 eV below the conduction band has been attributed to the isolated P-In defect, while the second trap, which is observed only for Bi containing samples at 0.08 eV above the valence band can be attributed to Bi clusters in InPBi. This acceptor level was proposed to be responsible for the observed partial compensation of native free electron density in InPBi layers. It is also shown that the deep donor traps are active in photoluminescence (PL). A strong radiative recombination between donor traps and the valence band are observed in PL spectra at energy 0.6-0.8 eV, i.e. similar to 0.47 eV below the energy gap of InPBi, which is determined by contactless electroreflectance