Влияние нейтронного облучения на спектр дефектов с глубокими уровнями в GaAs, изготовленном методом жидкофазной эпитаксии в атмосфере водорода и аргона

The results of experimental studies of capacitance– voltage characteristics, spectra of deep-level transient spectroscopy of graded high-voltage GaAs p+−p0−i−n0 diodes fabricated by liquid-phase epitaxy at a crystallization temperature of 900C from one solution–melt due to autodoping with background impurities, in a hydrogen or argon ambient, before and after irradiation with neutrons. After neutron irradiation, deep-level transient spectroscopy spectra revealed wide zones of defect clusters with acceptor-like negatively charged traps in the n0-layer, which arise as a result of electron emission from states located above the middle of the band gap. It was found that the differences in capacitance–voltage characteristics of the structures grown in hydrogen or argon ambient after irradiation are due to different doses of irradiation of GaAs p+−p0−i−n0 structures and different degrees of compensation of shallow donor impurities by deep traps in the layers.

Insulator-to-semiconductor conversion of solution-processed ultra-wide bandgap amorphous gallium oxide via hydrogen annealing

Developing semiconducting solution-processed ultra-wide bandgap (UWB) amorphous oxide semiconductor (AOS) is an emerging area of research interest. However, obtaining electrical conduction on it is quite challenging. Here, we demonstrate the insulator-to-semiconductor conversion of solution-processed a-Ga2Ox (Eg~4.8 eV) through hydrogen annealing. The successful conversion was reflected by the switching thin-film transistor (TFT) with μsat of 10-2 cm2/Vs. We showed that H incorporated after hydrogen annealing acts as a shallow donor which increased the carrier concentration and shifted the EF closer to the CBM.

Binding Energy And Absorption of Donor Impurity In Spherical GaAs/AlxGa1-x As Quantum Dots With Konwent Potential

In this study, the electronic and optical properties of single or core/shell quantum dots, which are formed depending on the parameters in the selected Konwent potential, are investigated. Namely, the effects of the size and geometric shapes of quantum dots on the binding energy of the on-center donor impurity, the total absorption coefficient and refractive index which are including transitions between the some confined states, and the electromagnetically induced transparency between the lowest six confined states related to the donor impurity are investigated. We have used the diagonalization method by choosing a wave function based on the Bessel and Spherical Harmonics orthonormal function to find the eigenvalues and eigenfunctions of the electron confined within the quantum dots which have different types mentioned above. To calculate the optical absorption coefficients and electromagnetically induced transparency related to shallow-donor impurity, a two- and three-level approach in the density matrix expansion is used, respectively.

Shallow Donor Impurity States with Excitonic Contribution in GaAs/AlGaAs and CdTe/CdSe Truncated Conical Quantum Dots under Applied Magnetic Field

Using the effective mass approximation in a parabolic two-band model, we studied the effects of the geometrical parameters, on the electron and hole states, in two truncated conical quantum dots: (i) GaAs-(Ga,Al)As in the presence of a shallow donor impurity and under an applied magnetic field and (ii) CdSe–CdTe core–shell type-II quantum dot. For the first system, the impurity position and the applied magnetic field direction were chosen to preserve the system’s azimuthal symmetry. The finite element method obtains the solution of the Schrödinger equations for electron or hole with or without impurity with an adaptive discretization of a triangular mesh. The interaction of the electron and hole states is calculated in a first-order perturbative approximation. This study shows that the magnetic field and donor impurities are relevant factors in the optoelectronic properties of conical quantum dots. Additionally, for the CdSe–CdTe quantum dot, where, again, the axial symmetry is preserved, a switch between direct and indirect exciton is possible to be controlled through geometry.

Impact of Surface States and Aluminum Mole Fraction on Surface Potential and 2DEG in AlGaN/GaN HEMTs

The presence of surface traps is an important phenomenon in AlGaN/GaN HEMT. The electrical and physical properties of these surface traps have been analyzed through the study of 2DEG electron concentration along with the variation of aluminum percentage in the barrier layer of HEMT. This analysis shows that from deep to shallow donors, the percentage change in electron density in 2DEG gets saturated (near 8%) with change in aluminum concentration. The depth of the quantum potential well below the Fermi level is also analyzed and is found to get saturated (near 2%) with aluminum percentage when surface donor states energy changes to deep from shallow. The physics behind this collective effect is also analyzed through band diagram too. The effect of surface donor traps on the surface potential also has been discussed in detail. These surface states are modeled as donor states. Deep donor (EC − ED = 1.4 eV) to shallow donor (EC − ED = 0.2 eV) surface traps are thoroughly studied for the donor concentration of 1011 to 1016 cm−2. This study involves an aluminum concentration variation from 5 to 50%. This paper for the first time presents the comprehensive TCAD study of surface donor and analysis of electron concentration in the channel and 2DEG formation at AlGaN–GaN interface.

Effect of magnetic field, size and donor position on the absorption coefficients related a donor within the core/shell/shell quantum dot

In this study, linear, nonlinear and total optical absorption coefficients related a single shallow donor atom confined in semiconductor core/shell/shell quantum dot heterostructure are researched in detail within the compact density matrix formalism approximation. For this purpose, firstly, the energies and the wavefunctions are computed by the diagonalization method in the effective mass approach. Moreover, the effects of size modulation, donor position and magnetic field are analyzed. The numerical results indicate that the linear and nonlinear parts of the absorption coefficients related with intersubband 1s-1p and 1p-1d donor transitions undergo significant changes.

Defect controls by silicon doping in non-polar a-plane AlGaN epi-layers

Deposition of high-quality Si-doped crystalline AlGaN layers, especially non-polar-grown AlGaN layers, is critical and remains difficult in preparing AlGaN-based light-emitting diodes (LEDs), as the Si-doping-induced variations of crystalline structures are still under exploration. In this work, structural characterizations of Si-doped AlxGa1−xN layers were carried out by associating with examination of their carrier recombination behaviors in photoluminescence (PL) processes, to clarify the physical mechanism on how Si doping controls the formation of structural defects in AlGaN alloy. The obtained results showed that Si doping induced extrinsic shallow donor states and increased the densities of point defects like cation vacancies. On the contrary, Si doping suppressed formation of line defects like dislocations and planar defects like stacking faults with suitable doping concentration. These results may guide further improvement of UV-LEDs based on AlGaN alloy.